Massive hug to you 
I had no idea what HG even was until I had it myself, and honestly people just do not get it. When you can’t even keep a sip of water down and people tell you to eat ginger biscuits… it’s enough to drive you mad! There really isn’t anywhere near enough awareness or understanding of how brutal it is.
I have a positive story for you, as well as a whole load of sickly solidarity!
I found my midwifery team weren’t particularly proactive and ended up having to seek help myself. Luckily my GP prescribed Xonvea and it genuinely helped so much, although it seems to be a postcode lottery because of how expensive it is to prescribe. The side effects can be rough, but if you can push through them it can make such a difference.
I also got a lot of support from Pregnancy Sickness Support — I used their WhatsApp service a few times just for a shoulder to cry on and it honestly helped so much speaking to people who actually understood.
Try to help yourself in any way you can and avoid every trigger possible without guilt. One of mine was literally opening the clean dishwasher, so my DH completely took over that job. Don’t commit to plans, avoid people who minimise what you’re going through, and just focus on surviving day by day. Stock up on any foods or drinks you can tolerate and eat whatever you can, whenever you can.
How are things with work? Are they being sympathetic and supportive? I know that side of things can add so much extra stress when you’re already struggling just to get through the day.
Everyone’s experience is different
but for me the sickness eased a bit in the third trimester, although other things like SPD got worse... One thing I really want to reassure you about, because it caused me huge anxiety when I was pregnant with HG — it stopped the minute my baby and placenta were out! I could drink tea again immediately. It was the strangest thing, going from one extreme to the other almost instantly. The relief was incredible.
And honestly, it absolutely was worth it. During the worst parts of HG I questioned everything because my head was such a scrambled mess from being constantly ill. But the second they put my baby in my arms, it was a million trillion times worth it and I truly believe you’ll feel the same.
Also, if it helps at all, I found the newborn stage so much easier than friends around me did. Sleep deprivation had absolutely nothing on 24/7 nausea. I actually felt relieved once he was here.
You are doing amazingly, even if it doesn’t feel like it right now. 20 weeks feels like such a long time when you are in the thick of it but you are half way through already!