Aw!! No worries, your little Mickey is just growing into a man, and is losing his baby teeth! They start losing their baby teeth around 4-6 months and the adult teeth will grow in their place. Did you find them or did you just notice they were missing? They are usually hard to find because most of the time they just swallow them!
Yes, it's absolutely normal. Around the age of 6 months, both cats and dogs lose their teeth present a youth and get their permanent adult teeth. If you notice any prolonged bleeding, however, that warrants a vet visit.
They do get sore gums, but most likely you won't notice except that they'll chew more - that helps relieve the pain. You can buy kitten toys especially for teething at the pet store, some of them you can put in the freezer (just like you would for babies that are teething) and the cold would help numb the pain. If it gets really painful, they might stop eating, and that would warrant a visit to the vet, but again, most of the time they just get through it with no problems!