Is this your first pregnancy lil?
If you aren't having any pains (well not any, it's mostly period-like ones or a feeling of tension in your uterus that is worrying) I'd say you're perfectly fine.
If you're having any pg symptoms (not all women have any at this stage, mind), you should worry if they ALL suddenly stop.
Otherwise you're fine.
TBH unless you see bright red, fresh blood it highly unlikely you're miscarrying.
And there have even been cases when women who were spotting red, or even properly bleeding, went on to have normal pregnancies. Alhough I must say such cases aren't very common.
Brown or pink spotting is a bit more tricky, sometimes that could be a sign of a miscarriage or an ectopic pregnancy but in many a case that's normal, too.
I spotted brown twice with DS, at 9 and 11 weeks, freaked out both times (previous miscarriage :() and was referred for an early scan. This time round, I was spotting like hell from about 7 to about 10 weeks. Did go to a GP, but because I wasn't too panicky they didn't refer me :( I'm currently 19 weeks and all going well so far.
In fact, yesterday when DS was sitting in my lap he got a swift kick in the nuts from his younger sibling! So hard he felt it through his very thick joggers! 
So I suggest, if you have more spotting you're worried about, go to your GP, BIG IT UP, and hopefully they'll refer you. Mind they're highly unlikely to send you for a scan until you're at least 7+ weeks because it's often too hard to see anything yet and the heartbeat may not yet be heard.
You could also try a private scan if you can afford that (here in Herts it costs around £60-80) but again, they may be unable to see much this early on.
Best of luck, but TBH you probably have nothing to worry about :)