Congrats on the progress you've already made! That's great!
I kind of went through similar growing pains after I started riding but before I felt truly comfortable riding with a large group. Luckily, one of the bike shops directed me to a route that I felt safe doing on my own. It was mostly country rodes and was used pretty often by other cyclists. I must have done that ride at least 3 times a week for about 6 weeks. It gave me the confidence to finally do club rides. I'm lucky in that our local club's rides are marked so if you can't keep you, you at least won't get lost. Plus, they attract enough riders of all levels that it's really hard to get truly dropped.
Are there any other riders from your class or other friends that you can do the club rides with? Surely someone in that group is in a similar boat. Do you get route maps for the club rides that you can follow in case you get dropped? You might ask around at your local bike shops to see if there are any other groups that informally meet to ride.
Live with intention. Walk to the edge. Listen hard. Practice wellness. Play with abandon. Laugh. Choose with no regret. Continue to learn. Appreciate your friends. Do what you love. Live as if this is all there is.
--Mary Anne Radmacher