FIL!!!

My father in law has really pissed me off and I need to know wether he was the A**hole or if my pregnancy hormones have me overreacting! A little backstory so it makes sense … me and my partner used to live in our own flat, private rented when I was 9 weeks pregnant the landlord told us we had one month to find somewhere new to live as he was going to be selling the flat, we where really struggling financially and to find somewhere in short time so my MIL and FIL said we could go live with them to get ourselves sorted (we didn’t really want to because as nice as this offer was there’s always a catch with them) they are the kind of parents that feel they can tell there grown son what he can and can’t do and now try to be heavily involed in our life decisions, with little time we agreed and gratefully accepted there offer a week after handing our keys in and moving into there place they tell us we will need to pay £600 a month to them (me and my partner full time and his 2 year old daughter on weekends) we didn’t expect to live there for free but that was almost double our flat and we still had to buy all our own food on top of it we tried talking to them but they said it was that or leave.. we lived there for 4 short months in that time I had a baby at 25 weeks and knew I couldn’t take her home there on oxygen and feeding tube as I knew they would have too much to say as they already did and she wasn’t even home! it felt like an eternity there was so many things in that time but my god I’d be here all day! Anyway a week after moving out ( 6 months ago) a letter for me for a debt of £180 went to there hosue they rang me screaming at me that a debt had gone to there house I told them I was really confused as I wasn’t in any debt, I rang the company straight away and cleared up the misunderstanding. It was a credit company (Argos card) I had took out bought something and paid it off in full as a way to try bump my credit score they found the payment and apologised… that was that Today i get a text saying “you can come round this afternoon you have a phone call to make while your here” I asked them what it was about and they said a letter came for me and they opened it and it’s a debt I have to sort …. I replied asking if it’s the same one as I know I’m not in any debt and if they can send me a photo they haven’t replied I sent a follow up message asking why they had opened my mail without asking me and he replied “because I can it came to my house” Just curious to know other people’s opinions? I think it was out of order to open my Mail and I think it’s pretty rude the way he’s spoken to me and the fact he’s telling me I have to go to there hosue and make the phone call Infront of him jsut feels wrong! I am a grown women and he’s not even my parent! … I changed everything over and changed over my address on the electro roll too i got a letter saying it wouldn’t be changed till April but wondering if this is why it’s gone there? They are not happy my letter went there but I don’t know what else I can do about that!