Strange hours to eat...

So I am 18 years old, im 5’1” and I weigh about 135 lbs. I used to weigh about 110 then when my boyfriend and I got together about 5 years ago, I’ve gained the weight. I used to eat whatever I want and never had a problem with it but now its horrible. I feel like I eat all the time. my usual day consists of getting up at 8 am, doing homework and eatting some oatmeal and toast and being to work at 11. I dont take lunch until about 3 pm and then when I get off at 8, I feel hungry again so I eat again. I feel like im eating too much or something just isnt working out for me. I dont look horribly overweight either, I mean I can tell and I think my butt is getting bigger and I hate it! please help