Please read :) Seperated from husband.. no longer trying to concieve.. buuuut

So I had the Mirena IUD removed over a year ago.. I was trying to get pregnant with my husband at the time but it was very difficult. We did have a few DR appointments because my cycles are very sporadic.. my period pretty much happens NEVER. My doctor thinks I have PCOS. To give you an idea: I have only had a total of 2 periods in the last 9 months, both random timings, & lasting 3 days. Yes I was taking pregnancy tests monthly to see if I was pregnant. All negative.

So anyways, I left my husband a few months ago.. details as to why does not matter. Anyways, I didnt rush to go back on birth control because I didnt have a sex life after my husband. DIDN'T being the key word. My doctors appointment for me to be put back on birth control is not for 3 weeks, so I'm curious, what are the chances of me getting pregnant with unprotected sex in the meantime? (I mean it wasn't happening when my husband and I were trying very hard to get pregnant for months.. so I kind of figured it is still very unlikely that I will get pregnant within the remaining weeks before I am put on BC).. however.. I met someone, I did have unprotected sex for the 1st time with a new partner 10 days ago.. and surprise, I had pink discharge in my panties this morning.. the first blood i have seen in months!! Here's what went through my head "Seriously is this implantation bleeding? After all of that time of trying to concieve with my husband & no luck?" Ugh. Im so irregular so this could just be my body deciding it wants a period again. Who knows. But i will be blown away if i am pregnant from the very first time i have sex after my husband & I seperate. FYI, my new partner & I both took steps to be checked for STI's before having sex so I am not concerned about any infections. We just wound up in bed a little earlier than expected. (Takes a long time to get in to see my family doctor) hence not being on the pill yet. So my questions to you are:

1. How soon do you recommend taking a pregnancy test? (because it's not like I can wait to have a late period)

2. Do ýou think this could be implantation bleeding?

3. In your opinion: How high of a chance do you think it would be that I get pregnant considering how irregular & almost non existent my periods are?

The person that I had sex with returns from work in 10 days.. so I would like to be able to have a negative vs positive test by then. We will be using condoms to be safe until i am put back on the pill. My doctor believed my chances of pregnancy with out fertility aid were low to begin with, so im thinking that I am just scaring myself. But the timing is weird right? I'll just be really shocked..if the first time that I have sex, after leaving my husband, I get pregnant. Am I being paranoid?

Thanks for reading!