Vivianna,
I completely understand & have been there. It's a miserable thing to be in daily fear. Really take into consideration the odds of you having a brain tumor though. (pretty slim chance) Aside from that, occasional sharp stabbing pains in your head are common anxiety/stress symptoms and as for your leg going "weird" you mentioned if you work too much it happens. That makes me think it's probably muscular in origin or possibly a nerve being temporarily impinged. If it was brain tumor related I'm thinking your symptoms would remain constant regardless of physical activity.
Tell yourself "I'm okay!", work on your deep breathing & relaxation techniques. As I said, I've dwelled on this exact fear for too long with the stabbing head pains & the whole nine yards too eventually having a brain MRI that showed no brain tumor
When your leg has symptoms next time try stretching it. Remember, the more we dwell on something the more we can usually feel it ;-) I just don't want for you to worry unnecessarily for so long like I did.
I hope you get relief from this fear soon. Keep us posted.