I'm 35 weeks and 3 days by my own dates by the doctors and my scan I'm 36 and 3 days. Can masturbation make me go in to early labour?

Hmm there is something that midwives do which is called a "sweep" where the womb is stimulated by a lubricated finger..
Im not sure that masturbation could do that unless you really prodded about...
Don't forget, your cervix is lower now.!

Having sex will encourage labour as semen contains a hormone called cyntosin (I think that's it) that stimulates contraction!

Masturbation is fine, just as sex is, unless your doctor or midwife directed you to refrain the last few weeks (usually only the case with a history of premature labour, placenta previa, or recent bleeding)

A membrane sweep, that glowstone mentioned, is more invasive. An area of the amniotic sac is actually moved away from the cervix.