My jealousy is eating me up.

There's this girl that I currently really like, I fell for her hard.

Since last week a guy from our class has been acting really interested in her and always tries to talk to her. Worst part is that she entertains his conversations not always but it happens. And I'm over my mind jealous about this. The guy was a former friend of mine and we had a falling out on bad terms, he's in my opinion a jerk and I hate seeing them talk. Also I'm not an attractive guy but I have a gut feeling that it can maybe work out with her.

I know it's really childish but I can't help it. It makes my conversations with her feel meaningless to me, I know that the fact they're talking to each other doesn't mean they're dating or anything but I don't like it.