B'Sha'ah Tovah!
Stains found on colored surfaces do not render a woman niddah. Stains found on tissues after urinating may render a woman niddah depending on how much time elapsed after urinating before wiping. Since you are uncertain of how much time elapsed, as long as you did not wipe immediately after urinating, you may disregard the stain on tissue.
The stain on your finger is more problematic. If the stain on your finger was definitely larger than a gris (the size of an American dime or Israeli shekel), and definitely came directly from your vaginal area (and not from touching the blood on the underwear or the tissue) then unfortunately it did render you niddah. You cannot attribute the stain to a possible scratch unless you know for sure you have a wound capable of bleeding (usually by having a doctor or bodeket taharah visually ascertain its presence). If the stain on your finger was less than a gris, or if it possibly got on your finger by touching the tissue or your underwear, then you may disregard the stain and were not rendered niddah by any of the staining you experienced.
If you were rendered niddah from the stain, since five days have already passed you may perform a hefsek taharah and begin counting the seven clean days immediately.
Many pregnant women experience staining, so it is not so unusual to have to go to the mikvah at this stage of pregnancy. Further, some women have a custom of immersing in the ninth month of pregnancy as a segulah.
In the future, you should continue to wear colored underwear and avoid looking at toilet paper after urinating to prevent becoming niddah from any further staining.
Please feel free to get back to us with any further questions.