I used to be very prone to getting colds and have in my time used most prescribed meds and can tell you, none of them work that well.
I don't know about Elderberries or Nettles (But I will be investigating them, for future reference) but here is what works for me.
You will need:
A means to boil water
1 Measuring jug
1 Jar of honey (cheapo honey is fine for colds, local sourced honey is better for hey fever)
Per day
2 Lemons
Per day
1 Orange
Per day
1 Lime (optional)
Per day
4 - 6 tablespoons of sugar
Per jug
A knife
A Spoon
A Drinking vessel
Boil enough water to fill the measuring jug, slice one lemon, half and slice the orange and lime, chuck 'em in the jug along with the sugar, coverwith half the jug of honey and pour in your boiling water.
Give it a good stir.
Let it brew for a minute or two, pour it into your drinking vessel, inhale the vapours it gives off through your nose and let it cool a bit, then gulp it down.
Repeat until the jug is empty, then sleep
If you have trouble sleeping, try an Irish coffee, heavy on the Irish.
On waking, give the used sliced citrus a good squash in the jug, slice up and chuck in the remaining lemon and orange and lime halves, add your sugar and honey, pour in you hot water and crack on with inhaling and drinking again.
If you feel peckish, chicken soup with lots of garlic and some crusty bread will sort you out.
Sleep again. Sleep may not be very practical, especially during the day, but if you can sneek off for a kip, then do so, as sleep is your friend.
When colds strike me down now, instead of feeling rotten for several days, after making the above I usually feel much better the next day and back to normal the day after.
It might not work for you (God knows there are plenty of cures out there that made bugger all difference for me) but as it is a pretty simple drink, with easy to buy ingredients, it might be worth mixing some up.
I hope you feel better soon.
Be brave
Colin