OK, if anecdata helps, then I never got mouth ulcers at all, hopefully you'll get lucky too!
I also never had much in the way of constipation, and no nausea. Honestly, I was incredibly fortunate given I was having massive doses and infused fortnightly instead of three-weekly because my tumour was so large. There really is no rhyme nor reasons as to how the side effects occur - another woman going through the exact same treatment as me had to be hospitalised with the vomitting, whereas I literally had not even the slightest nausea.
The side effects I did get, especially from the halfway mark onwards, were bone pain and exhaustion but not being able to sleep. The bone pain was just awful, and there is essentially nothing that you can do it alleviate it, except sleep which I had trouble doing. I ended up taking sleeping pills, prescribed by my oncologist, and they were a god send. I did though start taking tumeric - I would actually buy fresh tumeric and grate it into food or make hot drinks with it - and it did help somewhat, but to be honest sleeping through it whenever possible was the best relief.
I also had indigestion and reflux, for which I was also prescribed medication, but it was not that effective. I ended up sleeping in an armchair with built-in footstool that my husband bought and put into our bedroom so that we could still be close (bless). I also drank lots of milk and worked out what my food triggers for indigestion were so I could avoid them (weirdly bread and broccoli were the worst).
My hair fell out after my second round of chemo, just basically dropped out in the shower one morning so I had to have my head shaved. It was quite a shock, even though I knew it was coming. On the upside, I can tell you that there is nothing like the feeling of a hot shower pounding down on your bald head, I used to stand under the shower until the hot water ran out, it was so blissful!
It is great to try to be positive, but please PLEASE don't think it's a requirement. You have every right to feel shit - physically and mentally - and you really need to give yourself permission to be angry, sad, upset, worried etc. My son was only 4 when I was diagnosed and I used to keep it together for him - wanted everything to be 'normal' - and then fall apart after he went to bed. It's such a shitty time.
It will soon be over with, and I know it's hard to believe when you're in the midst of it, but you will get your life back. It might not be the old normal, but as I often say in many ways, for me, the new normal is actually better. I am focussed on things that make me happy, I don't put up with shit from anyone, and I spend as much money as I can on holidays as I know how bloody short life can be.
All the very best to you, and others in this thread going through chemo too. It is bloody cruel and hideous, but you can - and will - get through it.