The pump allows you to dispense insulin in more complex patterns, but the it won’t really get the job done if you don’t have a really good understanding of how many grams of carbs are in your food.
I’d suggest buying a food scale at a cookware store and spending a few weeks measuring portions on the scale and looking up the nutritional information. I use software from Lifeform. Fitday.com is another good source of nutritional information online.
You may find that the slice of bread you’ve been estimating as 20 g and dosing for 20 grams is really 35. That makes a difference in how far the insulin goes.
If you eat out a lot, it gets even tougher. I’ve been known to bring restaurant foods home and weigh them, and invariably they are always FAR more grams of carbs than I thought they were.
Alternatively, once you know exactly how much carb is in a meal you eat, you may discover that your insulin/carb ratio isn’t what you thought it was (or what it was a year or two ago.)
I don’t use a pump, I use shots, but over a couple years now I have been impressed at how often my carb/insulin ratio changes.
I have also found that my insulin often weakens as I go through a vial and my numbers will creep up as this happens unless I log everything and notice that I’m suddenly 10 or 15 mg/dl higher after eating a known meal than I would have expected.
That kind of stuff adds up!
Finally, if you are trying to cover a lot of carbs, well, that’s tough. Most of the people I know who get very tight control with insulin seem to cut way back on carbs–exactly how far has to do with your unique metabolism. But I can’t cover more than 50 g at once with any kind of precision and I do a lot better with less than that.