Help! My 15 week old won't eat

Anne
Hi,I'm at my wits end. My little one refuses to eat and I'm worried about dehydration.My son is 15 weeks tomorrow and we have been mix feeding (trying to build up to as much bf as possible. We were doing very well until now and now bf is down to nil, which I'm heartbroken about.)The situation is this. Last Thursday (till Saturday) my son started to be reluctant to eat but was his normal self, happy and active. I offered more feeds than usual and he got as much fluids as normal. Then on Sunday he refused feeds (both nursing and bottles) and while I tried to offer as much and often as possible he only got about 2/3 of his normal intake. He was very sleepy. He nursed a few times but only briefly before pulling off and crying. And arching his back. Same with the bottle.We took him to the out of hours gp because he also had a low grade fever. And he was diagnosed with a throat infection. They weren't too concerned because he still had enough wet nappies.Monday the same. Refusing to eat. Nursed even less. And he was very tired with. Low grade fever. I offer food often but he would only take between 40-60ml occasionally more.Tuesday I went back to the gp because he didn't produce enough wet nappies but now also had three loose stools. I got some dioralyte for him.Yesterday we didn't nurse at all. He fights the boob. Doesn't get anywhere close. He fights the bottle too. He temperature is now normal and his throat isn't as red anymore. But still he didn't eat. 
Also, yesterday he passed a very dry stool. He's just not getting enough fluids and I'm worried.Today is the same. My heart breaks and I'm in pieces. I haven't slept much since last week because I'm trying to dream feed him. Usually he would take more while sleeping but at night he also only takes about 90ml. Since midnight he's only had 300ml and it's noon now. He cries, screams and fights when I offer food. I'm so desperate and worried. I don't know what to do.Also I've been building up our nursing after many many problems and we got down to one bottle of expressed milk. Now I haven't nursed today or yesterday and only a few times since last Thursday. I don't have the time or energy to pump. I only have hand expressed to relieve engorgement. I feel this is the end of breastfeeding for us.But how can I get my son to eat more? What can I do?Thank you for your advice and listening. (Sorry for any typos! I'm on my mobile typing while holding my boy)