masturbating tips? idk.

i'm a 19 year old virgin and i think i have a problem with masturbating. i can start off really wet then during it, the wetness begins wears off and i don't know why. am i doing something wrong? i prefer clitoral stimulation btw. any tips?

i also realized that it's difficult for me to get wet when my period is about to start as well. could that be a problem?