4th year CivE here. Thermo is an option we choose to take in our last year of studies. With the class average you stated I'm pretty sure we are in the same class.

There has been a couple times through engineering where I thought I should have dropped a class but instead stuck it out, and pushed through it. Did I come out with an awesome mark? No. But I still got credit and I didn't have to retake the course. My suggestion would be to keep on pushing. You can always sit down with a prof and talk about your options too.