A lot of people get this, the inhalation of the smoke + the added affect of weed can cause this
Paranoia is kind of a mental thing, and it can easily mean that you're either a worry wart, or just possibly depressed (I used to have that paranoia real bad when I was depressed). These are both possible as you get older due to you getting less Testosterone, and other suck problems.
my suggestion is just stop doing it for a while. If you really want to get back into it, try it again like 2-3 months from when you quit. If you don't want to do that, try meditating and gaining better control over your mind and body. Accept the high and let it just take over and don't worry about it. But, a person who might be mentally not capable of that probably shouldn't be smoking weed anyway.