I tried some very potent weed when I was still relatively new to smoking and it gave me the paranoid feeling you are describing --I did not feel mellow or relaxed at all, I could barely move and 2 minutes felt like an hour. When someone spoke there was a huge echo effect, which was weird.
The stuff I have bought since then has been a lot less potent, but it gives me a very relaxing high and just makes everything I do more enjoyable (still able to function.) Maybe since you are a noob you should work your way up to the more potent stuff. Also, I smoked several times before I really got the high I was expecting, so don't give up.