yes or no third

Don't worry too much about the psychological effects of the age gap between your kids. Big and small age differences have their downsides and upsides.
If there's a small age gap, you might have the advantage that the kids can become playmates, same school, same friends...
But these advantages can also be the downsides because one child feels they get less attention compared to the other or because they both want to play with the same toys etc.
Especially regarding sibling rivalry, this is usually worst with an age gap of 2-3 years. If the difference is 5 years, there's usually much less rivalry towards each other. If the age gap is large, that can be a nice experience for the older child to learn to be caring towards others.

I think the most important thing is that you as parents are ready to go back to sleepless nights and taking care of the helpless little baby

Hey, we also had a long time of doubt. My kids are 11 and 8 years old, and now I'm 25 weeks pregnant with my third child. And we're very happy with this choice.

Here with 2 kids aged 7 and 10, and 5 weeks pregnant with the third. Suddenly full-on panic, though I guess it's probably the hormones...

Why full panic?

We're going for number 3 here too. Two kids, 10 and 8 now!

@Shanna I forgot to reply. Panic because I suddenly started overthinking everything that could go wrong and all the practical difficulties, plus a bit of shock that it was suddenly this real. We're happy and I think everything is going well. We were taking it step by step until we felt more certain about our choice, but then my cycle was off and it happened—quite special. We told the kids and they were super happy!

I'm also pregnant with baby number 3 here.
Our girls are 10 and 6

@ellen have you made a choice yet?
We're a few rounds further now and I'm starting to doubt myself too... so difficult..

Hey Ellen, we also hesitated about having a third child because my oldest daughter was 11 and my youngest was 8 at the time, but we went ahead anyway. We had a beautiful, healthy baby boy in November 2019, and now I'm pregnant again with my fourth child.