I hope this comment will be encouraging.
My husband and I were Protestant until 7 years ago, so we used condoms without even giving it a thought. Out churches taught that birth control was not only OK, but a responsible practice. So when my husband was in his mid-30s, he had a vas! Woo hoo, freedom!
So do you think we had sex every night? Or several times a week?
Throughout our late 20s and through our 30s, when our bodies were strong and smokin' hot to look at, we had sex approximately 1-4 times a month. More often than not, it was once a month; 4 times a month happened when we travelled home for summer vacation and our parents could watch our children for us!
Before we had children, it was about once a week, but once we had the girls, sex went waaaay down on the priority list. I was tired a lot, and my husband worked long hours, and we were super-involved at our church (evangelical).
We weren't happy about this, but you do what you have to do (or more accurately, you don't do what you don't have to do).
So if you're feeling bad because you only have 5 days a month, or 7 days a month, or, wowee wow wow, 10 days a month, it might make you feel better about it to know that a lot of people who use artifical birth control aren't heating up the bedroom every night!
Things got better as we and our children got older and things got really good when our kids were out of the house for good!
I have a theory that people who practice NFP are actually more sexually active than ABC users because they PLAN to use those "safe" days, whereas the ABC couples don't plan and therefore, stuff never happens.