Trying to conceive for a year

Hello We've been trying to conceive for just over a year after getting coil taken out just before our wedding . I normally have a 27/28 day cycle up until about March this year then things started to change. Cycles kept coming every 21 days then 20 then 19 up until 2 months ago my periods are coming every 14 days it's so frustrating as I know we're not going to get pregnant in that length of time. I've been refered to a fertility specialist as my blood tests are unclear as I don't know when and if I'm ovulating . We have a 3 year old son together but are desperate to have a baby brother or sister for him. Husbands been checked and he's ok. Any advice ? Quite nervous about the hospital appointment which is tomorrow . I'm currently on cycle day 16 and as of yet no period but keep feeling like it's going to happen .