Signs of Teething

What are some of the signs of teething that you've noticed in your baby and how early did it start? Marseille is almost 4 months old now and she started with the early signs around the 3 month mark (chewing on her hands, spit bubbles, excessive drooling, etc.) I currently breastfeed and supplement with formula. For the past two days she's been really fussy towards the end of the day and she won't take any bottles (breast milk or formula). She'll chew on the bottle nipple or she'll nurse for a few minutes and then start biting on my nipple. Could this mean that her first tooth is starting to surface? What products do you recommend to help with teething naturally?