Yes, it is definitely possible! Lochia typically lasts around four to six weeks, so finishing at four weeks is actually on the shorter end of normal, and your period can return quite soon after, especially if you are not breastfeeding or only partially breastfeeding. The tricky part is that it can be hard to tell where the lochia ends and the period begins, since they can look quite similar in terms of colour and flow. That said, if the bleeding seems unusually heavy, has an unusual smell, or you are feeling feverish or unwell, it is worth checking with your gynae just to rule out anything like retained tissue or infection. Most mums find it is just the body resetting, but it is always better to get it confirmed if you are unsure.