A blast from the past, what to do?

hi everybody, ok soo my ex that I dated for 4 years decided to appear in my life he decided to call for 4th of july we kinda started talking but like friends type of thing then I went on vacation and he would call me everyday I was pretty good at making sure for it not to go anywhere well now he is stationed in Tampa,FL which means he is only 4 hrs away instead of states away well the more I started talking to him the more my feelings came back for him soo since I was sooo confussed I just thought I should go visit him and see where things are at or where they go well things turned out great for the weekend but im scared for things to go somewhere cause its soo hard to trust him I feel as if I let him back in my life allits going to do is just cause pain on me but things just felt soo right and different but at the sametime I know I can trust him but its going to be sooo hard to he brings me the happiness I want in my life but at the sametime I feel like this him is only temporary what should I do??? just I just take things as they come or should I just forget about him??? anybody pls help let me know what you think I should do thank you everybody