I've been trying to gain weight using mass gainers. I've always been pretty small (around 106lbs at most) and now I weigh around 114. The reason I'm freaking out is because my boyfriend and I have had unprotected sex and I hadn't checked my new weight recently. I've been having back pain too, but it's more like Syatic pain. I haven't had any other symptoms and it's been about 2-3 weeks since we've had sex. Am I over thinking it?