My normal cycle is 25-29 days avgerage and my last cycle was 35 days&my period was very heavy & cramping worse could i've had a biochemical pregnancy?

Possible: Although early pregnancies such as biochemical pregnancy is a possibility, other possibilities such as ovarian cysts may delay your cycle. It is also not unusual to have an occasional abnormal cycle.

Early pregnancy loss: ...Is a possibility, but an abnormal cycle is more likely. Do a home test, if positive, see your doctor. Otherwise use Ibuprofen for cramps. Should symptoms persist in the absence of a positive test, you should be examined.