I can only speak from my own experience, and I hope that other experienced, confident childfree folks will chime in with comments relaying their experiences as well. Let's help out our fellow childfree folks who are struggling.
Here's what I have to say on this subject:
1. Nobody knows what type of life will make you the happiest more than you do, and don't let them convince you otherwise. Your mom might think she knows, but she's not you. Your best friend may love being a mom and assume you will love it too, but she's not you.
2. No childed person can authoritatively speak about childfree regret. Why? Because they have not experienced it and never will. The only people who can definitively speak about whether choosing to be childfree will result in a life of regret are mature childfree people. We've heard from Shelley who is 62, loves her childfree life and has no regrets about her choice. I am 44 and am more solid and convicted to my choice with every passing year. In fact, I thank my lucky stars every day that I had the courage and conviction to choose this life. I've not yet met a childfree person who has regretted the choice.
And let's not forget that while it's kept very hush-hush, there are parents who regret having kids. I've spoken to some of them and thanks to the anonymity afforded by the internet, hoardes of regretful parents are coming forth to spill their guts.
3. None of the people who are pressuring you to have kids will raise them for you. Enough said.
4. Being conventional, fitting in, being accepted and validated by others is great, but it's not better than living an authentic life. All human beings want to feel accepted, understood and part of a group and having kids provides a person with multiple forms of instant approval, acceptance and validation. On the other hand, choosing to be childfree provides no such validation (except from other childfree folks). This can mislead some people into thinking that having children is the easy route and choosing the childfree life is too difficult. Think again. Think about what is truly involved in having kids. Objectively observe your childed friends, families and coworkers and assess the total cost involved in being a member of the parent club. The cost is staggering and far higher than the cost of feeling invalidated which - in the big picture - is not really that big a deal. The trick is to find and develop self esteem and sense of self from within and not from external sources.
The cost of selling your soul to a life you do not want is the highest price a person can pay.
5. To develop conviction and confidence in your decision and to feel understood, validated and accepted, network with other childfree folks. Check out Meetup.com and see if there is a childfree social group in your area - join and participate! Same with No Kidding. If no group is available in your area, start one! Participate on childfree discussion boards. Read childfree blogs. The perception that you are an oddball and the only person who has made the childfree decision and experiencing these feelings of isolation and pressure is an illusion. There is an army of CF folks to connect with who have experienced (or are currently experiencing) the same feelings you are right now and they love to talk about it and support each other.
6. Adjust your attitude. Instead of wallowing in insecurity and believing the naysayers who tell you that you are wrong to think the way you do, look at it a different way: you are holding one of the world's best-kept secrets, and you're smarter than the average bear to have connected the dots and acquired it. Treasure it and be grateful that you had the presence of mind to think for yourself and be a free-thinking individual, instead of just one more herd-following sheep. Smile and let them wonder about you. Prove them wrong by standing tall and wearing your childfree status like a badge of honor. Relish in unnerving people.
7. It gets easier. The older you get, the more secure you will become in yourself and the less pressure and invalidation you will receive from the childed majority. More importantly, the less you will give a hoot what people think about you. It takes some time, but eventually people come to accept that they are not going to change your mind about having kids and - hey - you don't seem so unhappy afterall. Realize that most people have never met a childfree person before and haven't had any childfree role models, so we can't completely blame them for their ignorance and assumptions. YOU be that role model and set them straight.
And while you're at it, set the example for the budding childfree population coming up after you.