There are some articles online where persons had a parasite in their brain. I listened years ago news where a woman got a parasitworm into her brain, because she has eaten a snake and they are hosts sometimes, infected. Another case is a boy who was in a infected see.
It's similar to cats when they eat birds who are infected, they get worms or just swimming or trinking water that is dirty.
So yes it can happen.
I would not recommend going to any theRapist because they are actual a scam and just would give you gaslighting and psychiatric drugs.
I think you are not crazy but you should ask yourself closer from where parasites could have entered your body. Maybe you traveled alot, eat dirty food?
Another reason could be really just your wrong imagination. Maybe do you take any drugs or do you suffer from lack of vitamins or you have organic defects (liver, kidney) because they can give you destructive and wrong feelings so you are at risk to believe things that aren't there.
I think it is something like that if you where honest about your thoughts.
It can't be psychiatric disorders imo, because they do not really exist. Psychology is similar to religion, or synthology. It is not a science. Many who say otherwise are paid by pharmacy or very evil, or too naive and traumatized people who don't want to believe how corrupt and shitty our society really is.
You could go to a normal doctor (if you are not lower class or already stigmatized as crazy) an say you assume organic problems and you want a check up, blood tests, about inflammation, because you feel untypical tired lastly and anxious.
Mayby you hae the security to say the truth that you worry about parasite infection because you eat food or you came in contact with water who was possibly infected and you just want to make sure that there is nothing.
You could use chat assistant bots before you talk to a normal doctors, because normal doctors are often midde class and pro-psychology too so they would just ignore everything and stigmatize you as mentally ill, especially if you are female, black, homeless, poor, uneducated/unemployed.