Recently I switched to nights and I've found it difficult to maintain taking my birth control on time ( I've been on ocella for years). Before my bf and I started having sex I had one very brown only slightly bloody period for a few days. We had sex for the first time (protected) around June 12 and around June 23 I had very dark brown bleeding for about 2-3 days. too early for my period. I'm worried it may be implantation bleeding. I have been very tired and having back pain while working. I should of gotten my period a few days ago but it never came. I have yet to take a test yet. Should I be concerned?