I can go to bed bruiseless and wake up with bruises. I am A+ and very fair skinned.

That being said I am going to make an odd sounding suggestion. I suggest a blood test to check your androgen levels. I have PCOS and bruising is very common with it. If the result is within normal range you know you are not bruising because of endocrine issues.

It may not be the best accepted idea, but lots of bruising--and some unexplainable--with slow healing could point to other things.

The blood thinners idea (apsrin, etc) is very good too, and something I would look at first.