As others have mentioned the possibility of something more medical, I'm going to stray slightly away from that and talk about some more general things. The vagina, at all times, will always have it's own smell to it. In fact, depending on where you are in your cycle, the vagina may smell different. This is something completely normal for all females, and though it may be embarrassing, it's not something out of the usual.
In general, if you notice a sudden change in the smell, or if the smell is something you consider 'foul', then it may be something you may want to follow up on.
I would see if you have any other signs that may state that it's something more than just the normal body changes. Cramps, itching, abnormal colored discharge, heavier or different period, etc. In terms of discharge, something clear is generally normal (though it truly varies from female to female). In fact, again, during your cycle, the consistency and appearance of your discharge will change.
Again, if you feel that something is wrong, and that there has clearly been a change that you have never experienced before, then you may benefit from seeing a doctor just to be sure, which the previous to posts have explained.
As well, does the smell ONLY come after sex? Is it the possibility that the smell you are talking about is actually the lubricant that comes on condoms (if you use them)? (not to mention your natural lubricant also has a smell). As well, if it's been hotter these past days, it could just be sweat.
These are just a few other things that I thought were worth the mention. Hopefully things turn out best for you. Understanding your body is very important in determining when there's been an abnormal change... but then again, our bodies are always changing, so sometimes it's nothing to worry about.
This is your decision, if YOU feel something is wrong, remember, go with your gut instinct. Better safe than sorry.
And as a final note... try to avoid washing inside (if that's something you've been doing), as it can sometimes throw off the natural pH in the vagina and kill some of the things you actually need in there to keep things healthy :). Just something you may want to consider...
Best of luck!