Your OB can prescribe anything because they have that license, however, as Clysta stated, most likely not for a cold. I had a UTI and got antibiotics from my OBGYN, so if you need, you can get them.
You can see your doctor, but don't be surprised if he doesn't give you anything. Antibiotics are not used on colds for a few reasons. The main is that they won't work and the other is that the bacteria can develop immunity to the antibiotics, causing a number of problems down the road. Certain things such as ear infections, strep, etc would be things that require antibiotics and are all things that can be checked for.