I Am 20 Years Old And Have Had Very Regular

I am 20 years old and have had very regular periods since 11 years of age. I.was on deposited for about 8 months and did not have a period but it returned right when my last shot ran out and I became pregnant a few months later. I gave birth to my daughter in June 2014. And got the nexplanon implant in September 2014. I then got depo a month later and got the implant removed I was on both for a very short time. I didn't get the next deposited until the end of april and having had one since as I am married and were wanting to try again but this time when discontinuing mysterious have still not returned. I had a few spots of blood in September one day but never again and no period. Is this normal? Should be concerned? When will mybperiodsbreturn naturally?