I'm in a relationship and I masturbate:

1) a lot: Is about 3 times a week a lot?
2) occassionaly
3) rarely

I masturbate because:

1) my sex drive is stronger/more constant than my partners: Both
2) I simply cannot get enough sex/orgasms
3) I am not completely satisfied with/fulfilled by my sex life:

All of the above.

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Susan