I assume you're aware that people get funny symptoms after taking the morning-after pill? It's a lot of hormones.
And, not to say something really obvious, but take a pregnancy test on the slim, slim chance that the morning-after test didn't work.
Aww I'm sorry you're so stressed.
A lot of this could be from the pill. The hormonal changes in your body can cause your period changes, fatigue, feelings of depression, etc.
It's good that they are testing your stool, and doing some blood work.
The pinching pain might be stress, it might be an ovarian cyst. At your age, it is highly unlikely to be cancer.
Have you had unprotected sex? Have you ever been tested for STIs? Some of this could be symptoms of an STI, like chlamydia. You can test for those by peeing in a cup - you don't need to get an invasive exam for that.
At some point, you'll need a vaginal exam. Talk to your doctor and let her know that you have some trauma in your past, and that you'd like her to explain everything she's doing, step by step, and maybe ask if a friend can be in the room with you when you get your exam, if you're comfortable with that. Your friend can sit up by your head and hold your hand or something. You'll have a drape over your lap, so you won't be exposed or anything.
You don't need to really worry about that right now, though.
Since all of this started around the time you started taking the pill, I'd guess most, if not all, is related to that, and wouldn't worry. If your symptoms linger, or become hard to live with, talk to your doctor about switching to a different kind of pill, or maybe discontinuing it. It's not uncommon at all for women to have to try a few pills before finding one they like.