To @Maro:

If a pregnancy test from morning urine performed 23 days after protected intercourse came out negative, the result can be considered reliable. Also, the result of a beta-hCG blood test, performed 16 days after intercourse, should be sufficient to rule out pregnancy. It can take several weeks to a few months for menstruation to return after giving birth and finishing breastfeeding, as the hormones need to stabilize. If you have doubts, I recommend talking to a gynaecologist who can assess your situation and dispel your fears.

And when I did a morning urine test again 23 days after intercourse with protection, did it come out negative, or can I consider that there is no pregnancy? Should I repeat the beta from blood, even though I did it 16 days after intercourse? I will add that I don't know what phase of the cycle I am in, because my period has not yet returned after childbirth.
I don't know if he's not going crazy anymore. When can menstruation occur after breastfeeding?

In this case, there is no need to repeat the HCG beta test.

Negative beta hCG test results, taken 16 and 18 days after sex, are consistent and indicate no pregnancy, as beta hCG levels should be above 5 mIU/mL to confirm pregnancy.

And if I did a beta blood test 16 days after intercourse and it is negative, can I rule out pregnancy by combining it with this test after 18 days, which is also negative, or is it even better to go for a blood beta again?

Increased body temperature and lower abdominal pain can be related to various factors, including stress or hormonal changes. Stress can affect hormonal balance, which in turn can lead to symptoms such as abdominal pain or changes in body temperature.

If the pregnancy test you took 18 days after intercourse was negative, it is normal, especially if the test was performed under appropriate conditions (e.g. from morning urine) and according to the instructions.

If you still have doubts about the possibility of pregnancy or experience worrying symptoms, it is recommended to test the level of beta-hCG from the blood. This test is more reliable and allows you to unequivocally confirm or exclude pregnancy. In the case of persistent symptoms, such as lower abdominal pain and increased temperature, it is also worth consulting a doctor.

And what if I have had an elevated body temperature for a few days? The lower abdominal pain persists. Could it be related to stress or hormones?
I will add that today, 18 days after intercourse, I did a morning urine test again and it is negative. Should I go to the beta yet? Can I safely rule out pregnancy?