Hi again, Marlene.
Thanks for filling me in, so now I understand your complete situation with all your cats. It was a very smart move to have the male neutered, if that was all you could afford at the time. I understand how costly it can be to fix all your cats at one time; however, the organization I recommended in my initial answer (http://www.lovethatcat.com/spayneuter.html)
will help you locate a low-cost or free clinic that will spay your girls.
In addition to not having to go through this every
few weeks with them, you will also be protecting their health, as unspayed females run a high risk of developing a potentially very dangerous uterine infection called pyometra. http://www.sniksnak.com/cathealth/pyometra.html
Unfortunately, there is no over-the-counter anti-inflammatory to ease the symptoms of the heat cycle, which is safe for cats; your only alternative would be medication prescribed by the vet. So, if you feel your cat needs this, you'll have to consult with your vet and see what he/she has to say. I'm pretty sure they'll tell you the best thing to do at this time is to spay your girls.
The following organizations will help you find a vet to spay your cats, if the one above is not helpful:
As you can see, your local Humane Society and also your ASPCA, may also have suggestions for you, on how you can spay your cats using the vets they use, at little or no cost to you. Since your youngest cat was a RESCUE, please mention this, as they give special consideration to these types of cats. You can tell them they were ALL rescues, in fact!
is a credit card for vet expenses and medications, so if you apply for this, and are approved, it will help you pay off the vet fees in installments, making it easier for you, if you choose to go this way.
It would be great if you could explore all of these possibilities and then have your cats spayed. It would make them much happier and healthier!
I wish you all much good luck!