How do I tell him? Please help?

So I've been talking to this guy (Andy) that i like and he likes me too. We have dated before but it was a while ago. We hung out for a while Saturday but then another guy text me(Colin). I really like Colin and have never really talked to him so I want to see where this goes cuz I know he likes me too. But now that I am talking to Colin I just want to be friends with Andy cuz I've dated him before and I know how it will end and I want to see what Colin is like. I just don't know how to tell Andy that I just want to be friends. Btw I am only 14, Andy is the same age and Colin is a year older and I do know what I'm lookin for in a relationship.