LadyComp or BabyComp

Hello
We have 2 kids, and don't want any more at the moment, not sure in a few years!
It's 4.5 years since the last baby (they were 15 months apart!)
And i don't want to go on the pill or anything like that.
Have been very careful using natural family planning methods, i.e. temperature monitoring and predicting etc.
But i am not 100% confident with this, and do stress over it a fair bit, and it does affect our relationship a bit, i feel like i'm always saying no to hubby!
We are wondering about investing in a BabyComp or LadyComp, does anyone have any experience with these? or have any other ideas??
Looking forward to hearing from you all.
thanks