ADHD and losing interest in a relationship

I have been single for 3 years and during this time I have been involved in 4 relationships. Every relationship has a common theem I will work very hard to get the girl of my dream but as time goes by (4 to 6 months) I will get board with the relationship and brake up. 

I was diagnosed with ADHD 5 years ago and take meds but no counseling. 

I am trying to see if this is related to ADHD or my past marriage (a very bad marriage)