I'm feeling tightness behind my ears and a sensation of leaking fluid in my head after hair transplant. Is this normal?

You are leaking fluid?  Is it red (as in blood)?  You need to contact your doctor for an urgent follow up.  Pain is normal.  Leaking is not.

If your procedure involved Strip Excision (FUT), then tightness behind the ears is common.  One of the many benefits of FUE is there is no wound closure under tension, and so no sutures are needed.  Often this results in less post-op pain in the donor area compared to FUT.

The area behind the ears is having minimum elasticity and is prone to tightness following strip surgery. So, this is quite common but this feeling will decrease over a period of time. During the strip surgery, some fluid is given in the form of tumescence in the area from which the strip is taken out. Therefore, when you lie down on your head, it seeps out. So, routinely there is nothing to worry but still it will be better to go to your physician who operated upon you as he can explain it in a better way.