Stopping breastfeeding

So I've been having trouble lately with fitting nursing into my busy schedule. My baby boy is now 3 months, I work part-time, I go to school and I have a 5 year old as well. I have been pumping when I'm at work but because I only work half a day at a preschool it's getting hard to fit in. Plus my baby boy has started to spit up a lot more so I have been supplementing with formula at times and now he stopped spitting up. Anyways I'm slowly transitioning him off the boobs. But honestly I feel so bad. He's only 3 months I know I'm supposed to last a year. I'm worried about his health and I'm little bummed about losing the bonding time at such a young age. Just looking for some support here... am I doing the right thing??