I would slow down with the vitamins for now. That is why you have a dietician - they tell you what you need and when.
Just worry about getting better (day by day) get your proteins in - even if it's in small portions. Also, fluids - don't forget those.
My favorite drink that I found after surgery as I have mentioned before is Brambleberry tea from Starbucks. It goes down well, soothing and is chucked full of other good nutrients.
I still don't have a total eating regimen down, but I have noticed that every day is getting better and I tend to eat more.
My day may consist of eating cornbeef hash for breakfast - high in protein and also very soft to eat. Maybe try a softly scrambled egg with melted cheese - also high in protein.
I did not stay on soft foods long - maybe two days after surgery, than after that I was eating regular food. It's the stubborn Scandinavian in me - but it worked for me.
I also ate cheese, and that ended up being my best friend for several weeks - until I started to break off and try other foods.
Don't worry, your frustrations will come to a halt - mine are slowly disappearing as the days go by.
Also, I have read articles on gastric bypass that if you're not hungry - DON'T EAT! Which I've learned that the hard way.
Take your days slow with eating small portions, chew, chew, chew, relax - consult one of us for a shoulder to lean on, and get those fluids worked in.
Do not freak if you can't get all the recommended doses of food, drink etc... in one day. This all takes progression!
Handle what you can, and go with it.
Good Luck