Im sorry in advance im really bad at explaining my feelings or just my thoughts in general and english isnt my first language

Im a male btw 

Soo today is the big day apparently, i just got 18, new chapter is starting. But i dont know, i have a good life and everythings but everytime im alone or with friends i just feel emptiness, i usually just pretend to be normal or like being happy etc. Im not really excited about my birthday. Anyone has the same issue? Like sometimes ill be happy for like a day or two and then might feel sad a bit and then bam just no emotion whatsoever. I just feel tired and im trying to find whats wrong really. I have tried dating or well trying to have someone dating me but idk like ill be obssesed with them in my head overthinking tryna find if they like me or not or having mood swings rral fast just because of a scenario in my head, but once im in a relationship every feelings washes away and so i break up. i just wanna be "normal" i guess,  having something meaningful, trying sex etc but that stuff just dont appeal to me so even if i've had some occasions where i could have done it i just leaved. 

I dont know Im so tired man