Early period

So my husband and I have been trying to conceive for months now and it seems I m just not getting pregnant. We two children already which we conceived immediately when we had sex. Although we are not having as much sex as we probably should, I don’t feel that it should make a difference since we never had issues in the past. This month my period was lighter and shorter than usual and it came 3 days early. I have never been one to track my period until recently in December. Is an early period normal or a possible sign of pregnancy? I have two children I do not remember missing my period until after I discovered I was two months pregnant. pregnancy tests are negative.