'he works full time at a hard manual labour job so is understandably tired most of the time'
'dp would come and help occassionally at first...'
So he's left you to it, basically?
I understand what you're saying about his shifts and being in a manual labour job which leaves you physically tired... but - um - that's exactly what YOU have been doing since the baby was born too, essentially.
YOU work long (by the looks of it, completely back-to-back) shifts in a job which leaves you physically EXHAUSTED (because although you may not be carting bricks around or whatever, you don't sleep, which puts completely in the shade any job which is hard going but at the end of which you can REST AND SLEEP).
So - when both of you tired manual workers are home at the weekend, or when it's a night where your DP doesn't have work the next day, does he take on the night waking so you get at least ONE night of sleep to catch up? I'm guessing not. Does he take your son out for the day/afternoon?
Does he do ANY of the other shitwork - washing, shopping, cooking, cleaning? I'm guessing little.
No matter what job he does, this is not good, and he is not taking on the responsibiliy he should as a parent, and this is why you feel the way you do. So no judgement here, I'm afraid, but a lot of anger on your behalf, as I can sympathise with the situation you find yourself in. And the fact that it's highly unlikely you're going to be able to change your status quo to the extent that the division of REAL labour in your lives becomes fairer and lets you believe that 2 is manageable. Why do I say that? This:
'i did tell him i wouldnt be able to cope with 2, i explained everything to him but he said i was just panicking and in shock.'
How bloody complacent. Easy for him, eh?
Do you think you will be able to tell him what you have told us - and tell him that you will not be able to go ahead with this pregnancy unless things change? - that he takes on some REAL responsibility with the new baby, and your DS?
What would he say?
What would he do?
Would he say whatever it took, then when it's too late (when the baby is here) you'd be back where you are?
To those saying the deceit would destroy your relationship - that's quite likely. You need to think very, very hard. But it's no less likely that going ahead would also destroy both your relationship and your sanity, and this time with two children to consider.
Does he have the right to a say? Technically no, and also I'd say even less of a right given that he has proven that he considers all the work of childrearing to be your problem and your problem alone.
The point is you shouldn't have to ASK. A loving partner and a good dad SEES when you are knackered, when you NEED a night's sleep, and pitches in. They take the baby as they walk in the door so you can get away for an hour - lie down, whatever. They sort out washing or cooking or do a shop on the way home because they know this makes a massive difference to you and doesn't cost them.
I have to say - I don't know what job your DP does, but part of my attitude here is coloured by the fact that I worked on building sites for years. And I can assure you, the guys working on the plant, doing demolition/ pile driving/ whatever, are NOT spending the day bathed in sweat. Far from it...