Driving down the freeway and my car staled and wont start up again?

1998 Plymouth Neon car It don't start the First time I try to start it. It takes a little bit to get up to forty miles per hour once it does it runs kinda fine. I was going up a hill and it was going slow. but I made it up the hill and last night driving on the freeway with my kids in the car it just stalled on me. It wont start. I had to tow it to my aunts house. Some one told me its my fuel pump or my timing belt. can someone tell me what it might be. otherwise my car is a pretty good car low on miles. Its been doing this now for a month now any ideas please help thanks Shannon