Really strong pain, any ideas of what it can be?

It appeared today, is a really strong pain just underneath my bellybutton, and it hurts every time I stand up and walk and specially when I pee, it's an unusual pain, is sharp and I feel like if something inside me was pulling, I have not done any effort really and today I was most of the day sitting down and studying, if you know what it might be I will be very grateful for your help :)
Really strong pain, any ideas of what it can be?
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