I agree with Noorah - there is no reason for you to be sad. In this area, you were like a Tinok Shenishba.
Just to give you some perspective: for the future, you should keep in mind the Yehareig v'Al Yaavor nature of these aveiros. But, as for the past, what you did was an Issur Lav, for which Teshuva and Yom Kippur are Mechapeir, even if done intentionally. Kal vachomer in your case, where you were not aware of the severity of the Aveira, which means you were a Shogeig. Finally, some Rishonim disagree that these Aveiros are Yehareig v'Al Yaavor. The Ramban, for example, holds that they are Asur Midrabbanan. Regarding the past, you can "rely" on the Ramban and those who agree with him. But for the future, you are required to follow the Halacha Psukah, which you are now aware of.
Bottom line: Do Teshuva and move on. If you do so, you will receive complete atonement on Yom Kippur.
As for the future, you need to draw a line that you will not cross. For some that means no physical contact at all. Others are lenient regarding shaking hands, if the woman sticks out her hand first, in order not to embarrass her. See Rav Yehudah Henkin's article at
hakirah.org/Volume%204.htm. But that is the extent of the Machlokes - no one permits hugging, kissing, or holding hands. So, draw your line in the sand and don't cross it.
You may want to share this article with some of your relatives who are unaware of this issue. It appears to be far more comprehensive than most Wikipedia articles relating to Halacha, and will be less threatening than if you were to send them a copy of the relevant Siman in Kitzur Shulchan Aruch.
en.wikipedia.org/wiki/Negiah P.S. Keep in mind who the Chafetz Chaim was addressing. He wasn't speaking to those who are careful with these Issurim - that would be like telling the Steipler Gaon to avoid Bitul Torah. Rather, he was speaking to you - and to those like you - who are/were unaware of these Issurim. And you listened to him! Maalin, the Chofetz Chaim would be proud of you for taking his words to heart. I have no doubt that the Ribbono Shel Olam is proud of you as well. For what it's worth, we all are too!
Finally, by all means, follow Noorah's and Bardichev's advice, and seek guidance from a Rav.