Spotting? Miscarriage?

I’ve been spotting for the past 3 days, very light watery pink looking blood. It’s only really when I wipe. Never transfers on to a pad, the only time I get a bigger amount than a wipe is when I need to go for a number 2 and am straining. Soz tmi. Everyone I’ve spoke to says if it was a miscarriage it would have come by now and it would have got heavier ? not gradually come over 3 days. The bleeding started when I was at work and had done some heavy lifting (idiot I know). Please can you give me some advice on what you think it could be. Thankyou