Mother guilt trips me...

I'm 16, and of course I live with my mother. We have a pool in the backyard, and it's everyday now that she wants to go swimming.
I get it, it's just swimming, but even when I'm on my period or I'm sick or in serious pain (where it hurts to move a lot), she still wants me to swim with her. 
I have offered to sit with her and talk to her while she swims and that she can go swimming with my sister, but she says it's not good enough. I get that it's just swimming, but when I also have plans (that she has allowed) with other people, she says "If you don't swim with me, you can't do this and that anymore". 
She tells me things like "you're no help in the house" and even uses "if you really loved me you would". She has even started to fake cry before just to make me go swimming and tells me "Why don't you love your mother? Why do you hate me?". I feel like a horrible person now just bc I don't want to go swimming. 
I have gone swimming with her everyday for the past month, which has pushed back my time to do homework, study(my grades have gone down a bit), and do my chores since she wants to swim for hours, but when I want to get out early she won't let me. I have told her this before, but nothing has changed.