$80 a month is pretty tough to pull off.

Rice and potatoes mixed doesn't sound very tasty but I dunno what about rice and potatoes would cause diarrhea. Must've been the sauce you mentioned. Maybe you have a sensitive stomach.

I like potatoes fried in olive oil with some rosemary, oregano, salt and pepper. Add some minced garlic towards the end. Two eggs over easy and some grits.

Baked potato with cheese and chili on is a good bachelor meal.

Tons of stuff can be done with rice, arroz con pollo, steamed rice with salmon, stir fry, beans and rice, etc.

There are websites these days where you can type in the ingredients on hand and they'll spew forth a bunch of recipes for you.

The cheapest meal I typically make for myself is probably spaghetti. One quart can of sauce and a pound of spaghetti is almost 3 meals (2 proper meals + 1 half meal). Sketti's about a buck and sauce just recently shot up to $1.39. That's about a buck a meal, not including parm. Let's say a $1.50 a meal.

As for the diarrhea, I'd go for a GI checkup.