Medical bills with tricare?

We just started seeing a fertility doctor a few months ago. I made sure they took tricare, but I still have medical bills coming to my house. They aren’t expensive... but I thought insurance would still cover everything even with standard tricare? I’ve had blood work, a vaginal ultrasound, and an HSG test so far. From the paperwork it looks like the blood work cost $18 and the HSG was $30 after adjustments. I can understand the HSG bill, because it was at a different location. But I don’t understand why I was charged for blood work and not an ultrasound? Anyone know about this or experienced something similar? Thanks!