My best friend said she got with my ex and it’s been awkward ever since

My best friend and I been friends for 13 years. We grew up as neighbors. In high school I had a boyfriend. All 4 years straight. We broke up because of distance. I found out my senior year of high school that he cheated, but didn’t tell him that’s why we broke up. We continued being friends. 3 months ago I go to a party with my best friend and my ex shows up. I was trying to act like I was okay, but it felt weird. My best friend went up to him and they were talking. They exchanged numbers and I kind of felt weird. I texted her asking her what’s going on, but she said nothing. I tried to brush it off. 2 weeks later, they’re texting every day. They haven’t got together yet, but I’m awkward they’ll date. I don’t know what to do. I feel like I need to ask my friend something, but I’m afraid it’ll ruin our friendship.<br><br>Edit:I didn’t mention that it was a party where we went to college. Ex goes to that college. I go to a different one. We live in the same city so we could easily hang out still. I had no idea they were talking for a month. They went on a date last night and best friend asked me yesterday if that would be okay with me. I said it was okay, but honestly it’s not. Now I feel weird that they’re dating.