Can the beta hCG result 7 days before menstruation still increase?

It's hard to say. More important seems to be how much time has passed since ovulation and intercourse that could potentially lead to pregnancy. Although the blood test for the level of chorionic gonadotropin is very sensitive, it also has its limitations resulting simply from the physiology of fertilization and implantation of the embryo. It must take at least a few days after conception for detectable amounts of the hormone to appear in the mother's blood. You can find information that already after 7 days after fertilization, such a test can detect an increasing level of beta hCG. My opinion is that it is best to perform the test - from blood or urine - on the date of the expected menstruation, if it does not appear. I enclose additional information that may be of interest to you: https://www.gdziepolek.pl/artykuly/test-ciazowy-jaki-wybrac-i-kiedy-zrobic