positive pregnancy test 2 months after miscarriage/d&c

At my 9wk ultrasound on 4/18/18 there was no heartbeat and the baby measured 6 weeks 5 days. I had a d&c; on 4/24. I bled for 2 weeks after that. I got my first af on 5/25 and bled heavily for 8 days got a positive opk on 6/4. We bd on 6/4,6/5,6/6. I've been cramping since last week and yesterday I got faint positives on 4 tests and a digital. I'm still cramping today and l started spotting, it started light pink and then brown and then a bit of dark red. it's very minimal, but I'm now wondering if it's possible to have leftover hcg from the mmc causing the positive tests. Is it possible to ovulate twice and have a period and still have detectable hcg 2 months later? I had 3 perfectly healthy pregnancies and 1 miscarriage, but I never had implantation bleeding so this has me freaked out.