I know people don't want to read sad things about someone, but I have a need to write this . I'm 24(F), I am a student of medicine and I feel so low. I feel very depressed on and off for last year's, actually since puberty, it never ended. I'm not sure if anyone feels that way, is that normal or not. Last month , I'm on pause of faculty, I've been doing nothing honestly, just spending time home on social media, and I go out with my boyfriend 25(M) . We're getting married in August. He noticed my constant mood swings, he is supportive mostly, sometimes he tells me that he doesn't want me like this to be my whole life, I'm ruining his day when I'm low, but he still wants to help me.  Especially when we are around other people I act wierd and low. I'm not sure if I'm making things up or I have real mental problem. I feel stucked and don't know what to do. I was thinking about psychotherapy, but I'm not sure that I'm that bad. All In all, I don't have a real problem, just that feeling of sadness, pressure, and "party breaker".
Any advices? 
Sorry for my English, it's not my first language.