Declined Progesterone Shots?

At 16 weeks I was offered the 17P shot from my doctors. I assumed since they were offering, they had already checked with my insurance and it was covered. I told them yes, since I thought it was covered, come to find out it isn't fully covered and there is a $2000 copay 😳😳
There is just no way my husband and I can afford that right now, so we declined. My high-risk Doctor is stressing is so much though that it's making me worried. 
5 years ago I had my daughter 6 weeks early, BUT I feel like that was because of my lifestyle at the time (I was working 40+ hour weeks on my feet constantly only one day off, it was HORRIBLE) and my laboring Doctor at the time tested me and told me I had a UTI and that was deemed the direct cause of the preterm labor. 
My situation now has COMPLETLY changed, I'm a SAHM, and because of my previous UTI during pregnancy I'm checked WEEKLY for infection. I really think the risk of me going into preterm labor this pregnancy is EXTREMLY low. What are your thoughts, opinions??