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bpforever1
It sounds like you're trying to help your friend find a date, to the best of your ability, but it might be more helpful for you to offer tools for your friend to find her own dates online. You mean well, and you sound like an awesome friend, but in the end, your friend will appreciate your allowing her to grow in this area on her own. Perhaps you can help her with setting up online sites and tips for how to present herself online, how to protect herself from predators, etc. When she gets responses, you can help her with tools on how to respond, or how to weed out those who may not be a good fit for her. When she gets to the stage of actually dating, you can help her with what to wear, what to say, etc., by giving her choices and options based on her needs and desires, as well as what is often customary for first dates. If a second date occurs, you can help her with that, and so on and so forth.
As far as feeling guilty for talking to someone else online, I don't think you should feel guilty. Your intention initially was to help your friend, but now that you see how easy it is for you to get sidetracked, or how it could affect your relationship with your current significant other (even though your current partner and you are not committed through marriage), it might be worth being open with yourself and your significant other. You mean well in not wanting him to be jealous, but hiding things like conversing on a social networking site or dating site does not give your significant other and you the chance to grow in these areas together, and to see how well you both excel to the next level of your relationship - normative concerns and conflict resolution. If he is jealous, you can see if you feel comfortable with reassuring him and explaining. If that's not something you want in a relationship, you alone can ask yourself what this all means to you. Perhaps you found out through attending an online site for your friend that you actually enjoy exploring other options, and maybe you don't want to settle down yet. That is okay and nothing to be particularly guilty about. What you can do, in the interim, is prepare for a conversation with your significant other, when you are ready, and only after you have evaluated your own needs. Cheating can occur emotionally, not just physically (via sexual infidelity), which can naturally cause jealousy to ensue when the other finds out. But your intention is to not do that, yet your words sound like you may want to explore, but you don't know yet and don't want to cheat on your significant other. It's worth briefly mentioning to your significant other while possibly considering deleting your profile on that site in the meantime. If you feel that you want to explore other relationships in the future, you can always sign up again.
For now, I don't think you cheated on your man friend. However, it's good that you've acknowledged your feelings during this process and reached out so that you can take the next steps to figure out what is best for you, your relationships, and your helping your friend. Cheating occurs often because of lack of communication and a lack of breaking up due to feeling obligated to stay. Cheating occurs for many other reasons as well. Cheating can be prevented when we consider what is best for us as individuals and the relationship overall. Communication is best, but that is just my opinion. While there are some things that we can keep secret from our significant others, there are other things that are best to bring out in the open. This would probably one of those things. Who knows, maybe it might enrich your relationship with your significant other as well as the friend you're helping.
Others here might have better solutions for you to consider, as I'm single and asexual.