Above and beyond anything else, being as healthy as you can be before a pregnancy is really important. So, eating well, and eating a truly healthy diet is helpful (read: mostly fresh-vegetable and fruit based, low on the dairy and processed/friend foods, light on meats, salt, sodas, with plenty of easily digestible proteins, and lots of water). Being in -- and staying in -- good physical shape is helpful. Having enough rest, also very helpful. Making sure in advance that you are in sound reproductive health -- yearly pelvic exams, full STI screenings -- is also a helper.

Stress is also a big deal: it's possible that some of what you went through was due to the stress of being pregnant, especially if those pregnancies were unplanned or unwanted, and/or the idea f termination was stressful to you. Additionally, if, for instance, the pregnancies you had were ectopic, you had any other infections at the time, etc. the sickness is bound to be worse.

Morning sickness doesn't tend to be skewed to occur more greatly in younger women. But yes, it can occur for many weeks, and there's just no predicting that. And through a normal pregnancy, there are going to be a lot of times when you just do not feel good at all, when you're exhuasted, when you're gassy and bloated, a whole number of issues. So, that's something you'll just have to look at.

Of course, most women will tell you in retrospect that being pregnant posed a lot less challenges than labor and parenting, so.