I would say that the feces should be the least of your concern.
First of all, are you treating his regurgitations properly? If not you could just be setting him up for more regurgitations. You should be waiting at least 10 days to feed him after a regurgitation, but if it was my snake I would be waiting 14 days. However, because he is so skinny, you may want to just wait the 10 days. Then, depending on what size food he normally eats, feed him a food item half the size that he normally gets. If you could feed him a rat pinky instead of a small mouse that would be even better, since a rat pinky would be easier to digest that a fuzzy or hopper mouse. Also, it may be gross to you but if you make a small incision in the skin of the mouse/rat it makes the prey that much easier to be digested due to the snake's stomach juices being able to penetrate quicker.
You should also double check your husbandry. If the snake has only been in your care for 6 months, it was either too skinny or sick before you got it, or your husbandry is wrong somehow. This could be the main reason your snake is regurgitating, and if corrected the snake may turn into a ravenous eater.
I do agree that you should be taking this snake to a QUALIFIED vet. Any old vet won't be able to tell you much more than I just did, however, any vet should be willing to at least do a fecal to make sure your snake doesn't have parasites.
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alstiver@hotmail.com
Current snakes:
1.0 2001 Hypo snow cornsnake
0.1 2002 Pastel Ghost cornsnake
1.1 2002 Bloodred cornsnakes
To be added when it gets warmer:
0.1 1998 Het Hypo, Het Caramel cornsnake
1.0 2000 Hypo Het Caramel cornsnake