I'm 20 weeks preg. W/my last baby had preterm labor from 28 weeks on that began w/ pelvic pressure. I am again feeling a lot. Am I in preterm labor again?

Possibly. Having had an early, preterm delivery (ptd) w/ your last pregnancy, you are @ increased risk of having another ptd. Sometimes pressure is what heralds pt labor. You should alert your ob. Also, I would be following the length of your cervix; offering you Progesterone injections since 16wks; doing a test called fetal fibronectin beginning at 22wks.