[studentjunk]

Are you blanking the screen when you talk? If not, then you are likely touching buttons during the conversation. If that's the case, you have several options. You coudl install a program like S2U2, which has a setting to blank screen on talk, or use 'Touch InCall Screen Tweak', which has more options related to that. The latter is the one that I use on my phone, and I like it because it uses the gsensor and light sensor to turn screen on/off.

You also could just push the power button when talking, which blanks the screen but keeps the conversation going.