muscle strain or injury. help?

Simplicity

i have been doing the 30 day shred on and off for a while but am now doing it everyday for the whole of september.

Muscle on the inside leg going from top of knee to calf. Basically if you stand with legs together and knees touching then that point inbetween legs hurt.

Basically i don't notice anything when i am walking or normal day to day activities but when i do jumping jacks or 'butt kicks' the inside muscle of both knees sort of ache. if i try too hard they hurt. tends to be when i put weight on one leg at a time.

if anyone has any ideas on what could be the cause. i don't do any other form of exercising atm like running and i do the shred in running shoes with light clothing.
i don't want to damaged anything.
ps if i poke and prod my knee and leg i can't find any pressure points that hurt.

Thanks in advance.