After using lice treatment shampoo can i use my regular shampoo?

Not that same day, no. You need the residual to stick around a while to soak into the nits (eggs). Usually it's best to wait at least a day or so before you use a regular shampoo. Actually, if you only used one treatment, and you want to be sure of total kill- use a second shampoo treatment on the third day. Then a day later you can use your normal shampoo.