According to one of my pregnancy books, the PMS type cramps are considered a sign of early labour, but I don't think that they necessarily mean that things are going to happen too fast, unless they start happening quite strongly/regularly. I have had that type of crampy achy feeling almost every morning for about 1/2 an hour or so for the past few weeks, and my bub is no where close to being ready to come out! It would probably be a good idea to mention them to your OB/midwife, just so they know, and maybe he/she would like to do an internal to see if you are dilating, etc. too.
Since you have had an early baby, I think it makes another early baby a little more likely, but of course, only time will tell! All the best!