7 weeks in - and hair falling out when I shampoo? Also when can I use a gym and sauna?

It is best to contact your doctor about post operative care and instructions since each doctor has a different regimen.  In general, after a few weeks, you can resume all normal activities. 

After your HT operations it is necessary to wait at least a month before you expose yourself to heat and sports.  You might be having your shedding or it can be a shock loss. If ıt ıs shock loss than yoı should look up to fınasteride

Shock loss appears within weeks or months after a hair transplant in young men and the only way to prevent it is by using the drug finasteride