Well, there's no law saying you can't have more, although weighing the risks of going over that dose is important.
www.rxlist.com/ambien-drug/side-effects-interactions.htm It can increase many of the same symptoms we are trying to get rid of, so it's very important to carefully weigh other options rather than try to get more of a drug that doesn't seem to be working very well for you.
It would be better to find something that works better for you or try adding in a few natural things.
Are you taking/have you tried magnesium, melatonin, or things like herbal teas (Sleepytime, Sweet Dreams, or others) to help you get your sleep? Those don't usually interfere with any meds. I also use Valerian, but that can interfere/interact with some meds so you need to check carefully.