Not sure if it helps but I also had a weight gain issue. I started a bulk at the start of Feb weighing a hefty 157lbs
I hit the scales today at 174lbs, 17lbs gain in 54 days just under 8 weeks
What
I did was this:
07:00 Weight gain shake (mammoth 2500) @ 920 cals + Multi Vit
08:30 Sausage sandwich with brown sauce @ 450 cals
12:00 Subway roughly @ 950 cals
16:00 WORK OUT
17:00 PWO Weight gain shake (mammoth 2500) @ 920 cals
19:00 Lrg chick brst, Lrg portion of rice & separate Lrg Bowl of salad dressed in olive oil @ 750 calories
23:00 Bed
That totals around 4000 calories give or take. I know its far from clean and its not 5-6 small meals a day but it worked for me. I ate a lot of carbs which is key.
I dont think you should eat super super clean when bulking but try and keep it 60/40 split clean/dirty. But do avoid real dirty like Mac D's.
A weight gainer is a really good idea. Esp if you have stomach issues. And these guys are right there is no substitute for wholesome food but if you cant do it you cant do it.
Also while I was bulking I kept my work outs down to 3x per week but lifting as heavy as I could and no more than 10 reps per set.
I have IBS so I know it can be difficult but you can find the foods you can get away with. Trial and error.
So get a weight gainer, keep carbs high and drink a lot of water.
Paul
Oh and I used no supplements other than a weight gainer and multi vit, so dont bother with the halo you can gain without