Jane, I do not think an IUD will will solve your problem with menstruation.
For cost, you can also look at Implanon (3 year implant) for worry free birth control. The Depo shot is another option but make very sure you do your research before taking it. Your fertility may take quite a while to return after it.
Does your insurance not allow you to order a 3 month supply at once from their pharmacy? That way you cut your co-pay. You can also make your boyfriend pay for it

LOL, he is after all the one that gets the advantage as he does not have to wear condoms.
If you want to cut the costs of menstrual supplies, menstrual cups and washable (cloth) pads are the way to do it. On second thought, cloth pads will probably freak out the men in the house so stick with menstrual cups.
The disposable Instead SoftCup is the ideal product to solve messy period sex. It can catch up to 12 hours of flow and it does not interfere with sex or your vacation fun.
Best of luck and remember to stay safe!