It is time for your boyfriend to get help or go. Since your dad paid for the apartment, the move and the bed, I think it is fair to tell your boyfriend that the relationship isn’t working and unless he goes for some therapy individually or together with you in counseling, he has to leave. Don’t waste your time with someone who refuses to see their own issues and work on them.
You have the trifecta of indications that conditions will get worse if you don’t take control of this situation now. First you say you are trapped — staying in the relationship because you are afraid of his reaction or your depression through loneliness; secondly, although you are afraid to leave you are already having breakdowns in the relationship; and finally, you are noticing you are attracted to another person. These are the very ingredients signaling a need for change.
I encourage you to get some individual therapy first, and then give your boyfriend an opportunity to change or go. Waiting for things to get better isn’t a good option.