I've been with my boyfriend for about 5 months now.  
We met online through gaming &amp; very early on started spending a lot of time together (due to quarantine free time). So even though we've known each other for 6  months, we spent hours everyday doing things together, so our relationship progressed quicker than under different circumstances.  
At first when the relationship started, I was a lot more unsure. I'm not sure if I meant my first ever 'I love you' I told him. But after spending more and more time together, opening up more and communicating every issue, I feel like I have much more of a baseline.  
We have quite a lot of similiar values. Future life planning, hobbies, music taste, interests in what to learn. He's a very kind soul, patient, loves me very deeply, albeit a bit selfless to a fault and I trust him an amazing lot and really enjoy spending time together.   
But I've been having this nagging feeling all throughout our relationship. I've been constantly asking myself whether I truly love him. I keep thinking about things that worry me and where I'm concerned we might not long term fit together.   
I really want to do the right thing. I don't want to hurt him and me in the long run, I don't wanna have a relationship I might be in for the wrong reasons, I don't want to break it off later down when it hurts much more and we might have more plans together.  
I'm a naturally very judgmental person. I criticize almost everyone, sort them into a category, get irritated at small habits and can be unnecessarily cold and cruel, just to realize how nice they are an hour later.   
This is not exclusive to my boyfriend. I judge everyone I get to know better, even my best friend. I would have mean thoughts about them and insult them (in my mind).  
On the flip side, I can idealize someone just from surface level.  
So sometimes, I devalue my boyfriend by a lot and have these very unfair &amp; cruel thoughts that I could do better, I shouldn't settle, etc.  
The problem? When I think about doing better, I almost always think about surface level ideals. I don't think there is anyone on this world I would find flawless enough and perfect enough to never question my love and want to push them away.  
Based on the fact that I would criticize anyone around me, even close friends, I don't think true love would make me NOT have these thoughts. It's my nature.   
As for my nitpicks :  
Sometimes, I feel like my boyfriend lacks understanding for me and a certain 'depth'? I tend to think about stuff a lot, I like to watch more meaningful movies and intepretate them, get lost in them and have this void I want to fill and truth I seek. My boyfriend is a more generally calm person, not the overthinker I am, doesn't have as much 'depth' but on the other hand, he gives me a certain stability. But what if he just doesn't understand? What if we have no intellectual connection? I sometimes question his intelligence, even though he does often make smart decisions and can say insightful and intelligent things.  
We have a similiar kind of humor, but sometimes it feels like he can't perfectly hit the mark. He makes me laugh, but he lacks a certain wit. I make him laugh a lot and enjoy it, but I'm worried his humor might eventually fall flat for me.   
Then I sometimes get annoyed at innocent small things. Just his usage of certain smileys makes me feel like he is childish, like it doesn't really resonate with me. But it's also very sweet, he's a very sweet person, and I know if he sent me more dry messages, it'd probably make me feel more unloved. So I don't know what I want!  
Basically, I sometimes get this deep urge to tell him I love him, feel a lot of appreciation and warmth towards him &amp; I trust him a lot. On the other hand, I nitpick about petty things, worry so much and can't even know for sure if I truly truly love him.  
I don't know what's reality anymore. Am I splitting on him? Do I feel genuinely unsatisfied? Am I a critical asshole person that projects low self esteem and a need for perfection onto others?  
I don't want to make the wrong choice. My boyfriend is very nice, madly in love with me and is dead sure he wouldn't find someone as amazing as me &amp; wouldn't be able to love again. But I'm very sure that with his nice nature, he can find love again. If I had to let him go, it would hurt a lot, he gives me a feeling of security and actual interest in me.

 I really enjoy spending time together. He has a much more patient and calm nature, gives me mental stability and is more positive and emotionally open. He greatly values loyalty, communication and trust, we always discuss our issues. But when it comes to BPD, not even I myself understand. How could he?

I love him, but do I love love him? How do I even know? Is it possible?        

  
I'm unsure because as I said, I went through this kind of devaluation process with everyone close to me. Even my best friend, who I've known for a few years, I at first insulted in my head unfairly, minded the smallest quirks he has and criticized a lot of his behavior. Now after not being in intense contact for a while and looking at it from further away, I realized how valuable he is &amp; my platonic love for him grew tremendously.  
Is this perhaps a process I have to go through with relationships as well?