Gaining weight

I've been targeting to gain weight lately after losing weight which I really didn't intend to do. In the past weeks, my weight fluctuates from 81 which I was really worried about to 83 and hardly reach the 84 lbs. I didn't mind weighing myself anymore and today I remember to weigh again. I was surprise that my weight is now 85 lbs. Hmm Now I'm worried if I keep on gaining weight. 85 is my ideal weight but not more than that because of my height. I am still careful of what I eat like low fat ham and liverwurst with whole grain bread for my lunch at work and low fat milk every morning and evening. I try to avoid drinking soda after I had my UTI and now I'm used to drinking water specially the tap water. It seems that my taste buds becomes sensitive now that I'm not drinking soda everyday and only drink it twice this month because for me the taste is too sweet. I can now drink unsweet tea and add the no calorie sugar substitute but still I prefer not to drink caffeine. I guess what the Doctor tells me when I had my UTI now sinks in my brain that water is the best than anything else. Shen even told me to avoid the juices and just drink lots and lots of water. I'm wondering if water will make me gain weight. I hope not.