Cannot loose the tummy - how can I do it?

I am 47 years old, female, 5'9 and weigh (now 129-130 lbs). I was 125 -126 lbs and felt great at that weight. Although a minimal gain, I am bloated ALWAYS it seems in the abdomen. I do crunches (various ones), lift weights as well, in my minimal time. I am slim except for the tummy and also, I retain water so that by end of day, my ankle bones have all but disappeared.

I am a healthy person, but have extreme IBS..so maybe that is it, maybe it is age, but I am VERY frustrated with it and don't know how to raise my my calorie intake (I am lucky to get a 1000 calories in a day) to boost my metabolism without gaining anymore weight. I would welcome suggestions.