The answer to both questions is yes. You could very well be pregnant if the only form of birth control you are using is breastfeeding. If conditions are right I know of someone who got pregnant while taking the minipill and breastfeeding. You definately need to check. The other answer is yes, your cycles are regular but due to the suppressed estrogen levels you don't necessarily menstruate monthly. Some ladies spot, and many don't do anything at all, however we do ovulate so again pregnancy is possible we just don't know when.
I am not sure if this is helpful, but good luck to you and if you don't want to get pregnant please see your Dr.
K. @ The Nestingplace