Yes, high blood pressure can cause dizziness if your shower is to hot. Avoid hot water and heat. I don't know your circumstances so that is all I can say. Do you smoke, alcohol, drug's? This can contribute to dizziness also.
Yes, so people who have heart disease, hypertension, problems with their own blood vessels or blood contents, must be careful with sudden changes in temperature. If you want to take a shower, you must first wipe it, do not immediately flush it to the head so you can adapt first, so that you don't have dizziness and other symptoms. We must love our body because God has given us a perfect body. The pain that gives you is not God, but because humans themselves are not able to care for their bodies.
Make yourself cool by not taking a hot shower. That is for me the best thing to do. But of course it is also best if you will consult your doctor about your concerned.