Hi
I have tried to write guides with an eye to anxiety sufferers of which we have a fair number on this forum. Extreme weather and loss are always stress situations so what you are experiencing is pretty normal.
I would recommend that you read these links here. They have lots of very practical advice and easy to implement measures that can make a real difference for your own life and heat comfort. They have also real-life feedback from other anxiety sufferers during last year's record heat.
Pet Owners Anxiety - Practical Tips For Sufferers and For Supporters (worth a read for any anxiety sufferer or anybody in regular contact with somebody suffering from anxiety so they can help you better)
Hot Weather Management, Heat Strokes and Fly Strike (the biggest collection of possible and tested measures - most of them low foot-print and easy to implement. It is the combination of several little things that can make a real difference.)
Hot weather warning for the UK - plan now to keep your piggies safe! (This thread is from last summer when forum members tried a range of the measures from our hot weather guide, tested and adapted them for their own situation and reported the feedback. It is also a bit of a support Q&A guide for forum members with anxieties around hot weather. You may find it very helpful. )
Make sure that you counter your anxiety with planning at least one enrichment activity for every day so you create a positive memory and know that you are giving your piggies what they want from life each day: a happy today. Enrichment can be something very, very simple and free of cost outside of a cuddle, as long as you share the moment with your piggies. Enrichment addresses all the senses and not just cuddles and toys.
Do this even more so at times you feel stressed as a counter to your anxiety. Watching your piggies having fun is the best antidote and reassurance that they are OK.

I would also recommend that you take a picture or a little video and create a folder or a private account on social media. These activities create precious memories that will stay with you for your life and that will mean that you never lose your pets completely, even though you can no longer touch them. They are always with you in your thoughts and in your happy memories - and by recording those happy moments, you will be able to access them at any time when you are feeling down and overwhelmed and will be able to bring back some happy feelings and reduce your stress hormones.
Enrichment Ideas for Guinea Pigs
Now to the less enjoyable part:
The guides below do not make necessarily easy reading but they are invaluable for when you find yourself struggling with any of these aspects, from emergency/serious illness support to dying and grieving/coping with loss. I have made them as practical, precise and easy to follow as possible but they are also sensitive and supportive at the same time.
Just so you know they are there at any time and that you are not just left to fall into a black hole in the middle of the night when this forum is mostly silent.
I would recommend that you bookmark all the links in this post so you have them easily available at all times. I would also recommend that you tell your home support (family/friends) to remind you regularly to re-read them if needed.
Emergency and Crisis Care as well as Bridging Care until a Vet Appointment
All About Syringe Feeding and Medicating Guinea Pigs with Videos and Pictures
Caring for Older Piggies and Facing the End - A practical and supportive information collection
A Practical and Sensitive Guide to Dying, Terminal Illness and Euthanasia in Guinea Pigs
Human Bereavement: Grieving, Processing and Support Links for Guinea Pig Owners and Their Children
Looking After a Bereaved Guinea Pig
We have much wider information resource with lots of helpful as well as interesting information about life with guinea pigs and learning to understand better where they are coming from and what makes them tick:
Comprehensive Owners' Practical and Supportive Information Collection
I mainly hope that this will help to reassure you. There are lots of little things that you can do and that others in your situation have worked through and have given feedback on. There is also instant help for you whenever you really need it in extreme situations that talks you through all the little things and show you how you can work through them little step by step.