1. R' Ovadya Yosef wrote in Taharat HaBayit 3:7 that if a woman does not have a veset kavua, the couple are required to perform a series of three checks before and after intercourse to create a chazakah (halachic presumption) that intercourse does not cause her to become niddah. R' Ovadya explicitly states that external wiping is sufficient (although internal bedikot are praiseworthy).

While you did not check before intercourse, those three times that you did wipe afterwards, in addition to the two years of marriage in which you had intercourse numerous times and presumably did not begin bleeding afterwards, are sufficient proof that you are not "roah mechamat tashmish". Therefore, you need not repeat this series of bedikot.

2. "Roah mechamat tashmish" is a halachic concern that intercourse may bring on menstrual bleeding, similar to a veset haguf. Therefore, a woman who does not have a veset kavua must rule out the possibility that she has this other type of veset of bleeding caused by intercourse. By performing a series of three checks, a woman can create a chazakah that she does not have such a veset, and need not be concerned for the future, unless she later experiences bleeding after intercourse.

It is important to note that this topic is subject to major halachic debate. Most Rishonim do not hold that this chazakah must be created, and a woman would only be required to perform these bedikot if there is cause for concern, i.e., if she once experiences bleeding after intercourse, only then should she check before and after intercourse for bleeding. Therefore, some poskim hold that a woman is not required to create this chazakah in the beginning of marriage, and it is only necessary if she ever bleeds after intercourse. Other poskim hold that ideally a woman should create a chazakah in the beginning of marriage, but if she didn't, her experience with her husband is sufficient proof that she does not bleed from intercourse. Yet other poskim do require this chazakah to be performed later on in marriage if it wasn't done right away, even if the woman's experience has not shown that intercourse causes her to bleed.

Please feel free to get back to us with any further questions.