Is it possible

Is it possible to have period that avg 28 days then just magically jump to 38 days? AF came last month 9/10/17, this month it was suppose to come 10/10/17 (up until this point my period has always been regular.. 28 days lasting 5 days) took numerous hpt and they all were BFN. (last test was done on Saturday 10/15). Has this ever happened to anyone else? Was you actually pregnant when this happened?