Relactate

Ok mama's..my little boy is 2 months old...I breastfed and formula fed him til 5 weeks then switched to all formula after that. He had such a great latch, I just gave up to easily bc I felt like BF and pumping was taking my time away from our 4 yr old daughter. Now, I regret quiting! So how do I go about starting again? He already sleeps thru the night, will this affect his sleeping schedule? I nursed him the past 2 days instead of him using a paci and noticed I started producing just a few drops of milk! Also, I've already had my 1st period. Will this affect my periods? ( not on any type of birth control)