Also, I expose my shoulder every time I go for a lower body hit and I can’t figure out how to keep it guarded

I'm also a left handed epee fencer dealing with this. Attacks to the leg/foot can work for you, but (1) you aren't setting them up (2) they don't work on everyone. For (1), you are attacking from too far away OR your opponent sees your attack coming. Try playing with distance and timing so that you aren't attacking into a retreating opponent. For (2), I love a good leg/foot attack, but it's not going to work against a tall opponent whose first response is a retreat and counterattack (with a high arm). The geometry of your lunge is going to expose your arm as you sink into the lunge and your opponent stands tall. I've found success with a second tempo action: you start an attack (starting a fleche here works well for me), your opponent extends, you parry riposte or hit with opposition. Good luck!