Help!

Claudia
Hey guys!
So, I'm 24 years old in a serious relationship! (Hoping he'll just pop the question at any moment, haha!) anyway, we are sexually active but use precautions...condoms. I used to be on birth control but because of the extreme weight gain I leaned off of it with the suggestion from my endocrinologist. I was born without a thyroid , so I actually have to take my thyroid hormones every single day. Last week, I went away for business and forgot my pills (hormones) on my counter and was without them for about 5 days which is a lot! Anyway, my period is about a week late. I've gotten negative pregnancy tests, taken urine at home tests and even at the pregnancy center. I've been feeling some cramps but hen I'm just paranoid and sometimes think I'm making them up in my hhead. I'm freaking out! Do you think it might just be late? I'm nervous. I also did go on a tea detox earlier and lost a lot of weight within 2 weeks..not sure if I'm just letting my anxiety get the best of me or if I have something to worry about? The only other thing I can think of is that I might've lost my ability to be fertile. I've never missed a period before!