At 11 weeks, yes, your son is too young. Saber will be 4 months old in less than two weeks. Most peds recommend starting solids between 4-6 months, depending on their individual development.
Saber is a BIG baby-you can see from my siggy that he was over 9 pounds at birth-and right now he is about 16 pounds, give or take. Most babies are around 12-16 pounds when they start solids (some of the readiness signs is doubling their birth weight, holding their head up very well, and the loss of the "tongue thrust reflex" etc.) Saber has already hit most of the milestones-except for the birth weight-this is because he was alreary 1-3 pounds heavier than most newborns. He was nursing CONSTANTLY starting when he turned 3 months-and with all of the other milestones reached-she said it was fine for me to start cereal. Every baby is different, and reaches these milestones at different times.
Also-with this being your first baby, I wanted to add that it will take some time to get back to your prepregnancy weight-if in fact, you do reach it. Some women never get their prepregnancy weight back-they end up staying a couple of pounds over that-no matter what they do-simply because motherhood changes you. A young woman who was 116 may find the lowest she can attain healthfully after a baby might be 120, etc. Also, don't be in too much of a rush. I agree that you have not "plateaued". A plateau lasts much longer than a few days-more like a few weeks, or even a few months.
Give it some time. A common saying is "9 months up, 9 months down" when it comes to pregnancy weight loss. In my case, it usually takes me around a year to a year and a half to get back to "normal". Exercise helps-it really does. If you don't like exercise-then don't do a video or something you don't like. A simple stroll around the mall, or the park in nice weather with the baby in a stroller or carrier is nice-and ANY movement burns calories. Anything is better than nothing.