Hi im 38 weeks pregnant and i was using a dildo to masturbate and noticed in the toilet there was two big globs. is it my mucus plug?

Yes: Yes, orgasm can cause uterine contractions so likely there was some disturbance in the cervix that caused this mucous to dislodge. No worries, everything will be fine.

Most likely: And since u have had 3 csections, do not rec doing that anymore as it could make your water break or put u into labor before your c-section date an I am sure both you and your OB would rather not do a 2 am c-section unless necessary.