Ay, brownish discharge at 5 weeks is quite common actually, a few of us had it early on and paediatrician said it's usually just old blood, nothing serious lah. Since you're not having cramps and it's just a tiny bit, most likely okay je, but I'd still check with your doctor just to be safe, especially since it's your first time, better get peace of mind kan? They can confirm everything's progressing well with a quick scan, and you'll feel so much better after. Keep monitoring and jangan stress, first trimester memang macam-macam keluarannya sometimes.