Is what I felt after urinating considered urine, and does it transfer to the sofa, and does impurity transfer in this manner, knowing that I suffer from obsessive doubts regarding matters of purity?

Whoever is afflicted with obsessive whispers (waswas) is advised to completely disregard them. As long as the discharge is doubtful, being between urine, pure wetness, and vaginal discharge, and it is not confirmed with certainty that it is urine, then it is not considered urine and does not require washing. The place it touches does not become impure by that wetness. One must ignore satanic whispers and remember that the religion is ease. Allah Almighty says: "And He has not placed upon you in religion any difficulty" (Al-Hajj: 78), and He says: "Allah does not intend to make difficulty for you" (Al-Ma'idah: 6). Vaginal discharges are pure, but they nullify ablution.