I Have All Pregnancy Symptoms(nausea, Lower Abdomen Cramping, Headache, Morning

I have all pregnancy symptoms(nausea, lower abdomen cramping, headache, morning sickness, taste, etc) but all the blood and urine test I did came back negative. I missed my period last month. However, I noticed a linea nigra from my lower abdomen straight to my belly button.

I am confused. This is my first time of trying to get pregnant