Noted your history and understood the concerns.
It seems that donating blood and developing such symptoms like pain in abdomen, ear clogging, passing motion, dizziness
This looks to be a case of gastroenteritis
I would advise you the following in such a situation:
First of all take a rest in bed with lower limbs elevated above heart level and see if the dizziness goes away.
Take electrolyte solution.
Send stool sample for lab along with blood also.
You may need a PPI like Omeprazole
if nausea or vomiting.
Take an antispasmodic for pain in abdomen.You may need a course of an antibiotic active against intestinal infection if the tests are positive or you develop loose stools, fever, chills or so.
Consult your Doctor asap although this seems not to be related to blood donation
Hope I have answered your query. Let me know if I can assist you further.
Dr. T Chandrakant,