There are numerous reasons for premature rupture of membranes. The most important one is infection, which need not necessarily give rise to symptoms in the pregnant lady, before causing leakage. It is difficult for a pre term baby born at 28 weeks to survive, and if he does, he can have delayed milestones etc. Perhaps, God has spared you and the baby of problems that would have occurred later.
An incompetent cervix can be diagnosed before pregnancy and also, in early pregnancy. The cervical stitch is a surgical procedure done around 14th week of pregnancy with a success rate of roughly 85-90%. It is important that congenital malformations of the uterus be ruled out, preferably before pregnancy. Sometimes this malformation co-exists with an incompetent cervix. If such a malformation exists, the it may be corrected surgically (depending upon the malformation).
If you are suffering from hypertension, you need to be investigated thoroughly before next pregnancy to find out the possible cause, and see that the blood pressure is under control before attempting next pregnancy. I could not figure out the need to give you HCG injections.