If my mom & oldest sister have o+ blood. does that mean that i have the same type. can i donate blood based on my meds psych and whatnot?

Yes you can...: Only certain infectious disease, cancer, severe health condition prohibits you from giving blood.

Blood type: is genetic. A person may have the blood type of their mother or the father or a combination of the two. If your father's blood type was also O+, then that means that you will have O+ blood. O+ is the most common blood type. A person with anemia and/or bleeding problems should not donate blood. If you want to know your blood type, you can have a test done, but you would have to pay for it.