I can only tell you what my experiences were with chemo that had these same side effects. There was not the effective drugs for nausea that they have now. So that was a bigger problem. The constipation became a huge problem and continued for years after my initial chemo. If you can stomach it, whole grain oatmeal every day will help this, it might or might not be enough. I now mix up whole grain rolled oats and milk and kefir, add some blueberries and a touch of honey, I refrigerate over night and eat cold in the morning.
You can ask your oncology doctor for a consult with a nutritionist specializing in oncology if there is one in your area. They will have more tips and tricks for you to use. How are you feeling after your first treatment?