PIXY: You are right. I am looking to gain more muscle. To replace the fat on my body and make it muscle.
If you succeed, you will weigh more, not less. Take your focus off of your weight. Consider not using the scale at all, and just judging by how you look and feel, and whether or not your clothes fit.
In the best shape of my life, I was mountain biking so much that the action of balancing and maneuvering the bike under me had developed my abs, arms and shoulders as well as giving me tree-trunk thighs. I could eat anything, ride hard all day long, and hold my breath underwater for nearly 2 minutes. Nothing ever winded me. I'm 5'11", male and was about 22 then. I was in great shape. I was 155-160 lbs.
A year ago at 32, I was in terrible shape. I was getting no exercise, but still eating whatever I wanted. I was pretty easily winded, none of my pants fit at the waist anymore, I had the dreaded "love handles" and a gut. Not a big gut, I'm still a thin-built guy, but a gut none the less. I weighed 175 lbs. I made the mistake of buying new shorts.
Now I'm 33, I've switched from Pop-tarts to Weight Watchers Chocolate Muffins for breakfast. I drink a lot less soda, and swapped out Coke Zero for some of the regular Cokes I was drinking. Those changes alone cut ~500 calories a day! I've stopped buying ice cream at the grocery store, and stopped eating out so much and started cooking healthier meals at home. I've tired to get more exercise when possible, but most of the exercise I get is walking across campus to get to classes and chasing my 2 year old around. I've shed the belly, the shorts I bought a year ago fall off of my hips, the love handles are smaller. I'm still not what I'd call "in shape," but I'm much less out out shape than I was. I wish I had time to get back to regular riding, but I don't right now. I'm 165 lbs.
The point of all that is that weight is just a number, and kind of an irrelevant one, at that.