Early period or implantation bleeding please try to help?

I had hcg shot on the 3rd of this month, I'm on day 35 of my cycle with an average of 42 days.

Last night after sex with my partner I noticed some pink light blood when I wiped.

Today I had sort of like a light period but it's pink in colour and the blood is enough to fill half a towel in morning/ afternoon sort of like a light period then it got a little bit heavier in early evening and has now gone back to being really light like won't even fill half a pad in a few hours type of blood.

Bu I dont know because it's 6 days early and the colour is pink

I also felt sick/ gassy this morning and experiencing mild cramps lot less than period pain in abdominal area

We are trying for a baby we had sex at Ovulation time

Can someone please advise I don't know what this is?

Should I see a doctor or wait another week until my check up is due?

Btw my periods are always 41 42 day length cycles

The last shortest period iv had was in January this year at 29 days

So 35 days doesn't really add up to me?