Some people (including me, at first) have trouble maintaining the dream or lucidity while having dream sex. There's a simple solutions.

First of all, a little fact of LD's is that concentration on pretty much anything (hands, sounds, etc.) prolongs the dream, and at times also makes it more realistic. That's why it's a good idea to examine your hands in extreme detail if you realise you're dreaming (and not spinning; I don't know why it's so popular, it doesn't work nearly as well for some people.)

Now, during lucid sex, I don't know about you, but I lose pretty much all thought and plans, and can't concentrate on anything else.

No need. You can concentrate on feelings - textile feelings (touch), emotional feelings, as long as you try to experience them as vivid and as much as you can.

For me, once I tried that, sex no longer means the end of an LD. Hope this helps, peops.