Worried might be having early miscarriage.

This would be potentially my 4th baby, I have felt the same way I have in previous pregnancies for the past week, but wasn’t due on till today, so took a test Friday got a clear positive, plan was to see if the line got stronger today then ring doctors, my youngest is only 6 month old so wanted to make sure there wasn’t any health risks etc, anyway went and did more tests today for positive line to be extremely faint. Now I’m really concerned something is wrong and can’t stop myself feeling worried and stressed out, has anyone had this before, definitely going to ring the doctors tomorrow aswell, thank you xx top pic is Fridays test bottom ones are today :/ (bottom pic is all 3 together so you can see the difference)