I have a bruise on both of my shins that has been there for two weeks and wont go away. I am on lamictal 100mg twice a day should I be concerned?

Not necessarily. But talk to your doctor about getting blood tests done in particular a complete blood count (CBC) and pt, ptt, inr.
Bruise. Don t be concerned. A good exam and a few blood test should be reassuring if normal. Shin is very prone to bruises (its nature) due to exposure to get hit on it.