Unless you are already taking a huge amount of vitamin c, it may be prudent to increase your vitamin c intake. It probably is an autoimmune problem, however you might have something going on that is greatly increasing your need for vitamin c.
I assume you don't smoke, and don't get excessive sunlight, which can also cause collagen breakdown.
I was reading about how important copper is for collagen formation. So many people think they have excess copper and do crazy things like taking huge amounts of zinc. Imo you should have your copper level checked to rule out a copper deficiency. In the past I never thought that much about copper, but lately I am realizing how important copper is(it is part of hemoglobin, and is also needed for proper iron utilization). It is easy enough to overdose on copper, however imo copper deficiency is probably more common than copper excess.