Is it safe to use sleep aids or herbs to help my baby sleep better?

No. Never give your baby anything to try and help them sleep. This is extremely dangerous. Just because something is labeled an herb, or sold in a health food store does not mean that it is safe. It is never advisable under any circumstances to give an infant a sleep aide whether it be by prescription or over the counter.
No. Such items are rarely tested on babies. One should look for good research results when considering an herbal product or sleep aid. An effective product will have studies comparing the results of a group of children using the product with a same-sized group not using it. If all the manufacturer can show is a website and testimonials from happy users, then manufacturer likely has no good research.
No. Many studies have been done on sleep aids. No one has shown the benefit of medications in infants. Sure, you might get away with a night or two with your baby taking benadryl (diphenhydramine). However, the effect is not long-lived, and there may be side effects in your small baby that are not worth taking the risk.