It can be tricky. I always preferred to take my time and get to know whatever woman it was quite thoroughly, but sometimes they had other ideas. I guess the dilemma is, do you commit to them and risk living to regret it, or do you leave things open and risk losing them before you've made your mind up? I guess if there's much doubt about longterm compatibility then it's better to choose the latter. Either way it's a gamble.
It sounds like you're not ready to offer an exclusive deal yet. And it also sounds like you're expecting the next one you find is going to repeat what the last one did and try to rush you. That might not happen at all. If it does, I suppose the only thing for it is to be firm and explain that you don't want to rush anything. You'll risk losing them for courting too slow, which hurts, but isn't the end of the world.
Me, I always preferred to take things slow, but I was also usually very quick to shut out other women. I guess ideally it would be good to negotiate a temporary exclusive situation, and agree to review things after a certain time has passed.
I've felt for a long time that early sex is likely to cause trouble - staying platonic is boring and often impossible, but if it can be done then it mitigates the pain of going separate ways later on if that proves necessary. I'm afraid I was always rather weak in that respect, so it's hypocritical of me to recommend being platonic, but I think it's the best thing. Otherwise you can end up biologically bonded to the other person before you know them very well.
Just my 2 cents, and there are probably all kinds of different ways that people approach these things. Food for thought if nothing else.