Typical Seperation Anxiety doesn't occur until around 6 months old, and is usually when the infant realizes that their primary caregiver (Mommy usually) isn't there and it doesn't usually take two hours. For my son, it was immediate realization that Mommy was gone or leaving...
It sounds like your very young little one is in need of something that only you can provide...is he breastfed? Have you thought about his usual routine and what/when his needs should be met? Usually babies don't cry unless they need something, and this is what it sounds like your son is doing. At this stage, many infants are fed every 2 to 3 hours or on demand which for me and my son was every couple of hours depending on how hungry he was at the time.
At this age, I didn't leave my son to run errands(haircut was about it), but always took him with me. He loved being exposed to the sights and sounds of the market, the mall or the street for walks to the Starbucks. I understand needing a break, that time can be really necessary on certain days but, do you really need to be gone for more than two hours? Is there a way you can incorporate your errands and activities with your son?
I used the tips from Baby Center for when I had to go back to work when my son was one, and it was a tough transition but it worked out okay. I depended on Grandma until daycare was necessary for a few months, but otherwise I never left him with anyone he didn't have a bond with prior. It can be frightening for babies, especially since a lot of their comfort is based on the scent of those who they are 'familiar' with and have bonded to.
http://www.babycenter.com/0_separation-anxiety_145.bc#art...
I hope you can find a way to keep your little one happy, and find some time for you as well!
Good Luck.