I have these done evey 2 wks as well.... a lot of massage therapists have some training in preg massage. i get them to focus more on back, hips, glutes as that is where i am sore... i know they MUST avoid any abdominal massage if you ever have this.
I either lie on my side (s) or on a bed with the whole in the middle for the belly. I personally like on the sides better (hugging pillow and surrounded by pillows). I also do about 10 mins on my back with pillows under legs while she works on my head, neck and face for relaxation. It is also worth mentioning to the therapist which essential oils are no gos in preg as some of them are not aware...
enjoy it, i dont think you should be too worried and i find it really helps me relax and sleep and keep the aches at bay...

DH also gives me massages on demand - I am one lucky woman!! (a few of the preg books have guidelines for this which I left lying around til he read them and got the hint, he loves doing it now it is nice bonding)