My Battle With Imaginary Weight

so, i guess i've never cared about my weight before, i've always been thin and considered myself attractive. Recently i went on the pill and i think i've gained about ten pounds since. i know this isn't a lot and you can't really see it, my boyfriend tells me that all the time, but it's right before i go to bed and i stand in front of my mirror looking at every inch of myself that i decide i'm incredibly overweight. i honestly do know that it's not true, i check the online weight calculators, the ideal measurements and BMI charts constantly. They all say that i'm perfectly normal, but even still i feel unattractive and disgusting. I have even thought about breaking up with my boyfriend of three years just to get off the pill (I know this sounds incredibly stupid, but i'm trying my best to be honest, seeing as i can't be with anyone else). Anyway, i just really need to know if anyone else out there feels this way? Is this a common problem and even if you have no actual help to give me i'd like to know if someone else feels this way. i can't tell my friends and family, i don't even bring it up with my boyfriend anymore, i'm so embarrassed to be stressed over something that i always thought was so stupid. anyway, please let me know if anyone else feels this way, and maybe a few ways of coping with my situation. Also i am 18 and until now i have never had any serious issue with my confidence, i feel like I'm much too old to be struggling with something like this.