I am the case that 一個月內check到有懷孕. Because my body reacts and I have vomit, fainting, tired, breast pain, and a lot. When I go to see the doctor, they can't do anything as normally Home Pregancy test will show +ve only after 1 month( 2 days before M). If you really want to confirm, you can go to specialist who can do the Blood Pregancy test for you but that is expensive.
You can share why you doubt your are pregant, and let's discuss.