I’ve been lactose intolerant on and off over my whole life, but have been intolerant for the last 9 years.
I’ve done a lot of research on this as well.
Lactaid milk is NOT the answer if you are lactose intolerant. Why? Because it’s still got the lactose. All they have done is add the ‘lactaid’ agent to help you digest it properly, but you’re still inevitably putting the same lactose into your system and hoping that the lactaid agent works properly.
Soy milk comes in many varieties nowadays, and many of them are quite delicious. I prefer Silk myself, but Eighth Continent makes a really good one as well. I’d suggest experimenting with these.
As for yogurt, the live cultures are best in specific yogurts with extras of them, such as the LiveActive yogurt. I cannot digest these well myself, being very lactose intolerant. But they also make great soy substitutes. And soy is actually very good for you as well, so to substitute soy ice cream, cheese, and milk is great for your diet.
The lactose in milk that is not easily digestible in humans is the sugar content. If you check your cheeses from cow’s milk and find that they have a 0% sugar content, then you should be fine. Also, you can have sheep, goat, and buffalo products as lactose in cow’s milk is specific to cow’s milk. Based on it being the sugar content, the harder the cheese, the less likely it is to have lactose. If you react to these cheeses still, you might want to consider that it isn’t just a lactose intolerance you have, but something else.
Last, the only connection from IBS and lactose intolerance to psychological issues is that stress can cause it to be worse. I’ve found that whether I even KNOW if something has lactose in it or not, it bothers my stomach. But when I am stressed, my IBS and intolerance are heightened. But lactose intolerance is not a mind issue, as it’s no easier for your body to process lactose when you think about it or not, or even know about it. The problem lies in the digestive system. Everything in your body works better the happier you are, but your digestive system will still have an issue digesting lactose if you are lactose intolerant.
Lastly, a trip to a nutritionist could be a great idea. They treat allergies (yes, lactose intolerance is an allergy) at their core, and not only can you help that issue and perhaps eventually add dairy in moderate doses back to your diet, but it can also help solve any other allergy issues you might have (such as regular allergies, sinus problems, and more!).
Anyway… those are my suggestions based on my own extensive research and experience. Hope it helps.