E.,
I only read a couple responses, so I am sure I am repeating something you have already heard. First I want to tell you separation anxiety is completely normal at this age! There is no way to make it easier or to shorten the duration. All us parents can do is wait it out. Babies don't have a concept of time, so when you're gone for 5 minutes, it seems like you left them forever. Its tough, but its something you have to adapt to until it passes. It also comes around the time of stranger anxiety, so that's a double whammy! This baby thinks his world is you, and when you're gone, he is lost. Then he realizes there's other people out there besides mommy and daddy, and they smell, sound and act different. Also, a lot of babies this age are getting mobile and can crawl or they're experimenting with cruising and that's a huge adjustment. Its overwhelming for the little guy!
The first thing I noticed as I read was you said you joined "our gym" so I take that to mean your husband goes there too. Maybe try and get some "me time" and work out when your husband can stay with your son. This way he is still with someone who loves him and you get a break. That might mean only going 1 or 2 times a week, but as parents, we take what we can get :) I know your son is your number 1 priority and you don't want him to be miserable. Also, you don't want to be miserable. But honestly, you do not get "me time" until your baby is well passed this stage, then there's usually another baby that comes around! I was very proud that I was able to use the restroom by myself today, since big brother was playing with the little princess who has separation anxiety right now! That's what I consider my "me time". Another idea is to visit the kids room and just hang out there with your son a few times to see if he will relax with the workers and start to play, then gradually try to leave. Or maybe your husband can go too, and while you work out for an hour he's with the baby in the room, then you stay with him while your hubby gets an hour. If your husband cannot or will not watch him, try working out at home. Use dvds, or take him on a walk in a carrier or his stroller. There's also mommy and baby exercise classes you can go to, which will help both of you socialize. Then you can try again at the gym when he is older.
Now, I'm not trying to sound judgmental, but the second thing I noticed was your last paragraph seemed, well, a bit selfish. Yes your "me time" is important, but this is your child. He needs you. That's the mommy sacrifice we make. I'm sure you're fully aware that your hair and makeup routine has changed, your showers are shorter and that you only get to shave every other day now, if you're lucky. This is another one of those things. Just try and remember you can always go to the gym when your son is older and spending the night at a friends house or worse, doesn't want to hang out with you. I have to admit, I have to tell myself that sometimes when the baby is asleep and my son wants to play or cuddle and all I want to do is relax and read or be by myself. Hopefully your husband understands that you want some alone time and will watch him for an hour so you can go to the gym, or just take time for yourself. That way you get a break and your son still feels secure.
Best wishes,
V.