Uhmm. Well, you give him advice for his ex because you like to make him happy, but you dont want them together, and you do like him. Well, ask him who he likes more. Dont give him advice to get with his gf if it will only lead to them going back together again, meaning you'd be left out and everything. From what i understand is that he's kind of using you

Like, thats mean to take advice from someone when you're sad and then when everything is happy, you're not even in the picture anymore. I think its unfair and he would be ignoring you if you continue giving him advice for his girlfriend. Arent you jealous or something? I'd be, and this happened to me before. Tell him how you feel, make him promise that you'd stay close even if they are together, or make him get his mind off of his most recent gf, and go out with him again. Hopefully this helps.
Btw, you are a great writer. - Lana <3