Most Helpful Guy
Do not blame yourself about something like this ; you should on the contrary glad to see those feelings you are currently feeling.
Because they prove that you really did like you ex ; you were right.
Now, it's up to you. What do you truly want?
You gotta think for YOURSELF, not for him or his gf, and then work for what YOU want.
Have a great day
Most Helpful Girl
He's dating your friend? That's shitty and I don't blame you!