Not feeling confident probably means you are improving!
It is good you went back to dancing. Ask your tutor what he thinks about your level compared to the group class, I am sure he will re-assure you that you are capable of attending that level of class. Others in the class are probably feeling the same way that you do, but they may have a false air of confidence. Anyway, you are paying your money, go and enjoy yourself.
Don't let anyone blame you for their own failings. My wife occasionally goes to help a beginners Argentine Tango class, when I asked her about a certain partner she had danced with she said he was struggling but had insisted on blaming her for all of his mistakes! (My wife has danced with a four times world champion, and he didnt grumble!)
Do some homework if necessary, look at youtube, practice some steps at home.
Go for it, dancing is for enjoyment, and you need to enjoy yourself. If anyone thinks they have a problem with your dancing, the problem is theirs, nothing to do with you.
You will find partners you dance well with and others you don't (more frequently the latter!). I find some partners easier to dance with than others, and I am sure that a lot of people have problems dancing with me!
Walk into that next class with your head held high, do your best and enjoy yourself.
And please let us know your progress! There are a lot of readers of this board who have been there, done that and felt the same. They will be rooting for you.