PLEASE push the issue to get your liver checked via blood tests. DO NOT let this one pass. I was on 6MP for about
six months and had to get my blood drawn every Monday (yes, it became very painful and annoying) because my liver enzymes were elevated. It turned out that I had to come off of 6MP b/c my body makes some chemical that is in the 6MP (I guess only 2% of the population has this). It took an additional few months for my liver to return to normal, even after coming off of the 6MP. They almost had to biopsy my liver to see what was going on.
Nobody is going to take care of you better than you. Force the issue with your doc. It's your right and only makes sense. My Gastro doc was big on getting my liver checked from the beginning, and when we saw that my enzymes elevated it became a weekly withdrawal. You def don't want to damage your liver. Please call your doc and push the issue!
Take care and let us know how it goes!