Why no periods for 48 days with pain and fever at 27?

You might have hyperprolactinemia. What happens is this condition leads to the body producing too much of a hormone called prolactin, causing lactation and pain during sex. There are several possible causes, including some medicines you could be on; thyroid problems, or even a little tumor in your brain somewhere. I would advise that you see a doctor as soon as possible.

You can get pregnant during periods. It needs to be highlighted that it is possible for pre-cum to bear sperm so that is why the possibility is very low.  If you are pregnant, you may see symptoms such as nausea, and painful breasts. It could be down to missing your period and simple diseases like nausea and breast tenderness can be the first sign.

Yes, it's possible to get your period even if you have sex during your period. Getting your period is a natural part of the menstrual cycle, and it can occur independently of sexual activity. 

It's quite natural for some mild spotting to occur after intercourse, especially towards the end of your cycle. The dark brown spotting you got could be some of the blood from earlier times coming out. It is nothing to worry about, and it sometimes occurs when your body is getting used to the birth control pill. It will probably pass away by itself in a little while. 

The reason for the worsening of your periods and insomnia may be the hormonal changes from the surgery or the stress that comes with it. Period insomnia is a common problem that women face. You may also want to learn how to help yourself. Perhaps you could try some relaxation techniques like deep breathing exercises or relaxation baths. If it does not resolve on its own, seek medical advice as the best way to deal with those problems may be to find the one most suitable for you.

It is highly likely that you are not pregnant because you mentioned that the test was negative. Nipple pain could be attributed to hormonal changes, stress, or even caffeine. However, if you are still concerned, it would be wise to pay attention to your symptoms and periods. 

There can still be a chance of pregnancy. While the risk might be lower due to the short duration and no ejaculation, there's no guaranteed safe time for unprotected sex. Take a test to confirm.