Okay, so me and my boyfriend went out for about 10 months (I think) and then he broke up with me. I don't know why because the night before he said he loved me a lot... this happened about 4 months ago and I can't forget him! Now he is dating one of my best friends that he said he never liked! Please help me!

How old are you? Yes it's a hurting thing when an ex, and a friend get hooked up, but all you can do is to keep doing your own thing, and leave theirs alone. Did you know they were talking? If you didn't she isn't a very good best friend.

Aww :( I'm so sorry!! First of all.. I know exactly how you feel!! My boyfriend and I who I loved so so much broke up with me after about 5 months and I was heartbroken. I couldn't stop thinking about him afterwards! But I learned how to move on and thts what you have to do okay bye

You should try the no contact (NC) rule. Information about it can be found here https://www.askmehelpdesk.com/relationships/meaning-no-contact-nc-510419.html
If he broke up with you, there is always a reason, and whether not this reason may be unaware to you it does exist. He is obviously not the guy for you and your relationship was not all you made it out to be. Basically, you could do better. Your friend and your ex seem to have no respect for you or your feelings. So you should not waste your time on them.
NC can keep you from over-analyzing the relationship and slowly but surely eliminate false hope that may still exist.
I hope this helps.

I'm sorry, here's an easier link (https://www.askmehelpdesk.com/relationships/meaning-no-contact-nc-510419.html)

I'm having the same problem so what I do is, cry when I need to, laugh and try to forget and if that doesn't work, I hope I have a lot of junk food,.