Of course you could have 2nd or 3rd or more times of CPT, but you can only have less than 10 months (maybe 12 months - I could not remember it now)of full-time CPT in total, otherwise you would not be able to have OPT.
When I was in school, the ISS officer in of my college told me that I could not use CPT if I already graduated.But we all know that it is just like the words from USCIS officer, it might be wrong. And pjiang has said that he knows someone who did have CPT first and then OPT after the graduation.
Remember that OPT is run by USCIS, while CPT is sort of run by your ISS Office of your college. So, the best way to solve your problem is to go to your ISS Office. If they say Yes, then it is Yes. But according to my experience, for the same thing, you may get different answers from different officers. So, if one officer said No, then try another officer, until you get an answer of Yes.
And BTW, part-time CPT doesn't count anything, you can have them for years as long as you are in school, and registered enough full time credits in the same time.
In my last semester before my graduation, I was taking two classes as well as doing a internship job with full-time CPT. I got a permanent job offer.Other than the job offer letter, I asked this company to give me another letter, which says that they are going to offer me the internship, with the working hours (40 hours a week), pay rate, and with the start date, and the ending date (the date of my graduation). Those are the information that my ISS Office requested, then they would be able to apply the full time CPT for me.
Good luck.
