Why is my iPhone 5 doing this? - 1

I got my new and first iPhone in past May. Overtime I would have two or three pages of games and apps, and over 2, 000 pictures and videos. It has been about two months, so far all good, then it said I don't have enough storage when I tried to take a picture. So I deleted some apps or/and pictures to make room, and that would work. But the problem is, it has been doing this frequently now. Right now, I have 3/4 of a page (beside the very first one) and a little over 900 pictures. I can't delete any more pictures or apps. By going to the Usage in the General part of Settings, I can see that it says I have 13.5 GB. I don't know what to do to solve this problem. I'm on a limited data plan. Is this happening because of the limited data or is the iPhone messing up? Or is it just the way iPhones are?
Please, Please help me. I'm absolutely fed up with this problem.

Make sure what youre reading is the"available memory" and not your"capacity" which is a little easy to get them mixed up. From what you are saying it sounds like a low memory problem. It has nothing to do with your data plan.

It is not the phone and not the data plan. You are trying to put more on the device than there's room. Try resetting by holding in the home button and sleep/wake button at same time till you see the apple then release. I suggest importing the pics to a computer then deleting them from the phone to get some space then deleting text threads and emails to clear more space. Restart after you delete. Next phone consider one with more storage that would be better suited to your usage.