Honestly you might have both. For tapeworms, some symptoms that are unique to them is always being thirsty due to poor water retention and the main big away is seeing what looks like grains of rice in your BM. I believe it eggs. Roundworms can be a lot of different types of worms. Are you seeing small hair thin like white ones or large one about 6 inches long? Also, just what you are seeing is not necessarily your sole problem. The nice thing though with parasite cleanses is usually the herbs are in a broad spectrum against many things such as bacteria, fungi, and parasites. Therefore, you are taking care of more problems than one.
As for a doctor, normally their parasite tests are not that good. I've known a woman who put a worm 6 inches long in a test and it came back as "nonparasitic". I also tested negative three times in a row on a parasite test. If you feel you have the symptoms of parasites, then doing a parasite cleanse is probably a good idea. The test might only test for 40 parasites and there are clearly more types than that.