Someone help😩

So my boyfriend’s bestfriend is a girl who I used to be good friends with and lately I’ve been getting really jealous whenever they’re together idky tho. Last week we were in school and the way my schools lunch schedule is set up, there are 3 lunch waves, I had 1st lunch and he had 2nd. I was heading back to my class and when I got to the top of the stairs they were coming down. When my boyfriend waved to me, I rolled my eyes and kept walking. Later that day during our free period he asked me about it....I lied about the whole thing. I feel bad for lying to him but this same situation has somewhat happened before, were I felt uncomfortable with his bestfriend but in that situation she made him choose between me or her. I don’t want to do that to him. I love him so much, what should I do?