Hi Teaching Mum,
I am very sorry to hear of your baby's death.
Ectopic pregnancies do sometimes just "happen". The fact that you have no underlying causes, especially no history of infection, makes it much less likely that another ectopic would occur. Generally reoccurence is because both tubes have been affected by infection and/or scarring--for example, if the tube had been repaired then you would have had a greater risk of an ectopic on that side.
I know that this is a decision for you and your dh to make, but keep in mind that there are always risks for everything.
Your bitterness now is normal. Just let yourself feel whatever bubbles up. This is how we work through grief, and very painful it is. Over time, although you will never forget Jasper, the pain will become easier to bear. I know it is very difficult to go through now. You will get lots of support here at BB. HUGS.