Don't mix phentermine with clen, nor with ECA. Because, it can be dangerous. (VERY) So for now, stick with phentermine and see how you like the results, for it's hard for me to say how your body will react w/ phentermine + ECA, but I am factually sure that Phentermine + Clen. is very dangerous.
MaxBiceps, I talked to a friend of mine, and she's more up to date with phentermine. She stated: "Yes, you can cycle P w/ ECA for 2 weeks, than P alone for 1 week, than you can run clen for 2 weeks."