I haven't played minecraft in a while and now I can't get on.

When minecraft launcher pops up I click play, then it loads (sometimes only) to the page where its starting minecraft. I get onto a sever and I'm only on for about 20 seconds and then it all the sudden just stops, and disappears. Like the page literally, just ends and then I'm back to my desktop screen. I have tried so much to fix it but its really starting to make me mad. I haven't gotten onto minecraft for a pretty long time and now all I wanna do is play it with my friend again.