Confused

So I've been w my boyfriend for 3 months now and I love him I really do and my ex & I are best friends, but lately my ex and I have been getting closer everyday and there's these feelings but he is talking to this other girl and I shouldn't be jealous but I am because she's making him happy. All I want is for my ex to be happy, and he wants me to be happy, but it's so confusing he'll talk shit on my boyfriend, but he is so sprung on this new girl and my feelings are so mixed up right now and I don't know how to fix it. ))):