The endometrium of 0.3cm will not be menstrual because normally, there are different periods of endometrium in the menstrual cycle. Normally, the endometrium may be around 0.3cm when your period has just ended, and around 0.8cm when you are ovulating. If it is near the time of menstruation, the endometrium may be around 1.1cm, or even 1.2cm. If it is 0.3cm, with abnormal bleeding, it is not menstruation, it is an abnormal phenomenon. It is recommended to go to the hospital for an ultrasound examination to rule out any abnormality in the endometrium, and depending on the situation, oral anti-inflammatory and hemostatic drugs should be taken to help stop the bleeding and promote the recovery of the endometrium. At the same time, you can observe whether such a situation occurs next time, if there is still such a situation, it is recommended to take certain oral medication, such as short-acting contraceptive pills for regulation, to avoid this situation for a long time.