Oh good grief!!! MIL lives with you?
Yikes!!
Any of the specific items you mentioned can be stressful.
All of them together . . . . . . . golly.
Is MIL competent?
Can she drive, safely?
Maybe there's your driver for your teen-ager.
Or . . . . are any of her friends involved in the same activities?
Can you arrange car-pools for at least some of those activities/
About energy . . . . . have you and your husband taken any time away?
Together?
Even a short weekend get-away?
Are you familiar with Marriage Enrichment or Marriage Encounter?
Google either or both with the name of a large city in your area.
Meanwhile, a 15-year-old is certainly able to take over some of the household duties. You may want to have a serious sit-down meeting with her, addressing her as an almost-adult, and explain how thinly stretched out you are. Tell her some of the household duties you need help with.
Ask her if any of those seems like one(s) she could pick up with a little training and practice.
I'm thinking, in particular, of laundry, dishes, cleaning kitchen
and/or bathrooms, vacuuming, preparing some meals,
taking the trash out (to the curb?), etc.
Does MIL help with with anything?
She should.
Unless she's severely handicapped.
Will mention here that I've written all this
before reading any of the other answers.
Have you had a serious conversation with your husband
about your energy level, etc.?
Not in association with the sexual situation
but in general?
I may write more after I've read the other answers.
Good luck!