Missed periods, negative tests

I've missed two periods and took multiple tests all with BFNs(most recent was yesterday). I've been bloated a lot, my stomach has been feeling tight recently(as if I had just done a ton of crunches), more headaches, and more heartburn than usual, and more fatigue. I've also had more acne and my hair seems a little more thin than usual. I'm a little overweight, but otherwise healthy 20 yr old. I just want to know what's going on. Has anyone else had anything like this? Did you end up being pregnant, or with something else going on? Please help. I've been looking everywhere and only want to go to the doctor if I have something to worry about.