I've been lying to my partner for months about the stupidest thing
Are these the same issues that you have been talking about with your mother?
Yeah, my partner is a million times better than my mother as a person
You shouldn't lie to your partner. If they find out you have been lying they will not trust you in the future.
I will deal with this when I have to
You will have to deal with it sooner than later, so I think that you should just tell them the truth. Lying does more harm than good.