hi there, thank you for such a comprehensive history. You have not mentioned the diopters of the glasses that you use but I am assuming that you are myopic. In early myopes as you who had the problem at a young age, the sclera is quite thin and stretched out due to which the choroid or the the layer where the blood vessels are there in the eye is visible thro the whites and that is what you are seeing as the vein. If they are not causing any other symptoms other than cosmetic then you need not worry about them, the yellow spot you have described could be a ptrygium which is nothing but a tag of the normal conjuctiva which has bunched up near the limbus or the junction of the cornea
and the sclera. If that is not growing in size or encrouching on the cornea then it can be left alone or can be excised by the opthalmologist with a small surgical procedure, the choice is yours. I suggest that you maintain proper hygiene of the contact lens
that you use and visit your opthalmologist periodically to get your eyes and posterior chamber of the eye checked routinely. Besides that nothing else needs to be done,. I hope this helps, take care.