for period pain i usually take naprogesic. i've started on the pill because my period pain is rediculous, some days it hurts so much that i have to stay in bed for the day. i'm on Yasmin and it doesnt cause weight gain so that's not really an issue for me, but its only a low dose so i dont know how it'll go. Yasmin is a bit more expensive though, $22 for a months run as compared to some of the other Pills which you can get a 3 month dose for $30.
it's all hit and miss with period pain, you have to find out whats good for you. i'd say naprogesic, but there's always ponstan and higher doses of panadol which can work too. hot water bottles are a godsend.
edit: the Pill primarily causes weight gain because of water retention- the same reason you bloat just before/during your period.
and i just thought of another thing- eating a lot of fatty foods, caffine (like in coke, coffee, some chocolates) can make your period pain worse. medium/heavy smokers have a chance of worsening period pain too, dont ask me why but the doctor say-ed so.