I think im bisexual and I hate it

So I'll (21F) been questioning my sexuality for ages. I've never really been able to say if I'm interested in girls or not. My sexual orientation is always so confusing to me and I hate it. As of now I think I'm bisexual but it makes me so uncomfortable to say that. I only mention it to my friends and family now and then but they never seem to care about it and the topic always gets changed quickly. The worst part is that I've been in a relationship for 2 years and I dont know if I should tell them at all. I feel like I'll be cheating if I dont tell them because I can't imagine having a serious relationship and not being open about it. But being open and honest about my sexuality makes me anxious aswell.