It seems that you have multiple things happening in your life right now. Congrats on going vegan, it can be a hard step. As far as your weight loss, 3 lbs is near on track for healthy weight loss. Healthy weight loss is 1/2 lb to 1 lb per week. Losing weight at that rate likely means you will keep it off. Now, since you are still on steroids your body may lose weight more slowly, as steroid make you gain (as you well know I'm sure). As far as what you are eating, it all sounds great (don't beat yourself up over an occasional soda), but be sure to watch your portion sizes of grains and oils. While these are good for you, too much will still make you gain. Also, be careful w/ nuts, a serving is only 1/4 cup (same 'rule' applies as w/ oils and grains regarding portions). As far as the thrush and yeast infx's, have you tried eating yogurt w/ probiotics, or I have also heard acidophilus can help w/ that (although I haven't researched it or used it myself). Silk makes a vanilla soy yogurt w/ probiotics that is very tasty. Something to think about.
Just wondering: what has your doctor said about your diet change related to your illness and medications? (I am in health care and always find it interesting to see what health care professionals have to say regarding veganism). If you have not talked w/ your doc about the diet switch, please don't be discouraged if he/she doesn't approve or looks down on it. Many doc's (traditional Western docs) are not trained extensively in nutrion and the benefits that a vegan diet can have for the health of their patients.
Good luck to you!