Sounds like your hair was damaged. No, it is not safe to keep doing the process over and over again. It will only make matters worst. Once hair is damaged, it can not be repaired. You can buffer the damage with protein treatments and deep conditioning, so you can at least make your hair look good, until you cut off the damage. Which can take a really long time, depending on your hair length. And of course that also depends on the degree of the damage.
If the process was to be repeated, it can only be done on the new growth, NEVER on the hair that has already been processed. So you would need to wait about 4 months for new growth to come in. In the mean time you need REALLY good protein treatments. Not the cheap ones. They are in fact different. Protein treatments have to have the right molecular weight in order to actually penetrait the hair. Cheap ones don't have it.
Good ones are:Nexxus Emergencee (it is great for chemical damage) Redken Extreme, and Joico. You should do it one a week for the first 4 weeks, and then once a month after that. If you over do it, it will have the opposite effect. Hair with too much protein will become hard and break off. You must also deep condition after protein treatments, or your hair will feel like straw. Protein is not meant to make hair soft, conditioners are.
You should also attack it from the inside. Get yourself the biggest bottle of Omega 3,6,9 you can get. Also biotin and MSM. It will take 4-6 weeks before you see a difference, but trust me, it will be worth it. You can get those products really cheap if you go to Puritansale.com. Their products are of great quality and you can't beat the price.
So I hope this helps. Blessings and beautiful hair to you.