iphone 4 is overheating and draining battery

ok so a few days out of nowhere, my iphone started overheating and i noticed that the battery was draining faster than normal. the whole battery would drain in 4 hours or so. last night i did a reset on all settings and that didnt work. then i did a back up and restore and that didnt work either. i read some other posts that said to delete all email accounts and i also did that. i plugged my phone in last night and i woke up and it was off and only had 7% battery life. so i plugged it in again this morning and did another reset. i deleted apps and pictures and messages that i dont need. my next step is to go to the apple store but i just wanted to see if anyone had any pointers on what to do or try to do? thanks