First of all this is a very complicated area of discussion.
Ideally this would be addressed with a qualified therapist as there are so many issues involved.
I have always felt there is no such thing as too much sex as long as both people agree and it enhances, improves and strengthens your relationship.
A possible indicator of too much is when the relationship revolves around sex as the primary driving force.
IMO the most important, yet often the hardest, is to talk to your partner and have some in depth discussion about your thoughts and concerns.
"Everyone is entitled to their opinions and it is not my job to change their mind." Dali Lama