Hey! I have a non hormonal IUD too and sometimes I'm really all over the place. I was always kind of irregular but I used to have a much shorter cycle (often 17 days) but now sometimes it's 30+. If you've gone up to 35 days before a few more isn't much longer but I'd say if you can get an early response (can't remember the name) to get one ASAP. To calm your nerves and to make sure everything's ok
Also weight loss can mess with your periods and I think this is a common issue.
Good luck!