Feeling discouraged already

It hasn't even been a month and already I am discouraged. I weighed myself. I have gained 3 lbs this month. I didn't really change anything other than working out twice a week. How did this happen? I eat fruit, veggie sausage with one slice of potato bread for breakfast. I usually drink a cup of cinnamon tea also. I eat a salad with Italian dressing and maybe crackers or 1 piece of potato bread for lunch. I drink water only, no juice or soda. For dinner I fill my plate half full of vegetables, with a serving of protein which is either tofu or fish, and a very small serving of a carb. I don't know what I have done wrong???? I had lost 10 extra lbs after having my baby and gotten all the way down to 181.2 finally reaching my 20 lbs lost goal. Now here I am over a month after exercising weekly back at 191.2. I could seriously cry. I gained all ten pounds back even with a good diet and exercising regularly. I am so sick and tired of being overweight but days like this make me wonder if it is even worth trying anymore. I have been trying to lose this weight for 7 years. And for seven years it has been nothing but a struggle and constant battle no matter what approach I take. I either lose nothing, lose 1 lb a week, or gain weight.