Should I Feel This Way?

Ashii♏️ • Kik is Ashii_Kitty, feel free c:
My boyfriend and I have been dating since October but we've known each other and we were friends before. Recently he's been talking to me less and talking to another girl, and likes all her pictures, and has started hanging out just the two of them.. And I feel like we're drifting apart.. I'm known to be jealous, too clingy and dramatic at times, so I'm not sure if I'm just overthinking it.. I'm just really scared of losing him 😔 I don't know what to think of about it. I have a big fear of being alone and I don't have very many friends, and I can't stop thinking about how empty I'd feel without him... I need help. 
I also want to add that because I have such a low self esteem, I feel completely and utterly useless. The other girl is way more attractive than me, and I feel like I'm nothing compared to her. It's really starting to bother me, even though he says she's just a friend..