Today I woke up and my one testicle felt different and I've noticed it is harder than the other - I got a ultrasound about a month and a half ago and nothing was wrong - is it normal for one testicle to be harder than another on occasion?

If you are still having questions and concerns, talk with your doctor. Ultrasounds aren't 100% correct, things could have grown since your ultrasound, something could have been missed.....
Please talk with your doctor if you feel there is something going on.

Go see the doc again. Doesn't seem normal. Good luck!!!