No, I don't think you are being unreasonable, but getting stressed won't help, taking action might - so do all you reasonably can, and don't forget dietary changes, because there have been a lot of studies and articles recently explaining the part that farming animals for food has played and is still playing in this serious issue. Some sources put the contribution of animal agriculture to climate changing emissions higher than the transport sector.
I read recently that we need upwards of a trillion more trees to sequester all the excess carbon dioxide we've chucked into the atmosphere over the past 50 years, so we should all definitely get planting - either in our own gardens or via organisations like The Woodland Trust.
I think I am doing all I can at the moment, being vegan, saving energy, sourcing my electricity for a supplier that uses only renewables, hardly ever travelling by car, even more seldom by plane, recycling everything possible, composting all organic matter, keeping a wildlife friendly garden, never using garden poisons, being as economical as possible with water, buying eco -friendly and vegan detergents, toiletries etc. - but I am learning all the time about what else I could do and embracing it all willingly. The current trend seems to be plastic reduction, so I'm taking that on board too as much as I think I can. I often go out picking up litter - it could blow anywhere and all of it could injure wildlife.
It has been estimated that we could feed many more people than we currently do if everyone ate a plant-based diet - we already grow enough food, but most of it gets put through factory farmed animals first, at great cost to the planet. Perhaps we would plant more woodland if there were no animal farms. I can hope!
I am not convinced so much by the over population argument - I think it's over consumption that is more problematical - people in subsistence, rural Africa, even if they have large families, do not impact upon this earth in anything like the same heavy fashion as a family of 4 in this country. We also have to sort out world poverty if we want people to limit their family size - children are still an insurance for old age in many cultures that have no welfare system in place.
In rich countries, lifestyles count for a great deal, negatively in the main. We can't wave a magic wand, but we can all try our best not to be a larger part of the problem than we need be.