Please read very confused

So I starting TTC in Jan 2015, always had a 30 to 32 day cycle. Last month I was 8 days late and seems this month I am late again. It's been 5 days now negative hpt, no af, could it be possible my cycle has changed to 38 days now? I don't get how I can be like clockwork then change....It's messed me up as now I don't know when I'm due on. Advice would be appreciated