so I've been on the implant for probably around 4/5 months now roughly. since having it in, my periods have ended up being 2weeks long instead of 1. and have had random on and off bleeding after its finished until I next come on. only this month, I'm now 4days late. since having it I've never been late I've always started when I'm supposed to, so why is this random out happening??? could I be pregnant?? I know I must sound so dumb as its pretty difficult to get pregnant on contraception. just need advice