The OP mentioned the jewellery as quite rightly she thinks it's a way to deflect from him having to pay more for the shared living expenses. The ol' "But I bought you a Birthday present for £100 so I don't need to put money in the the electric" con. Because that's what it is Quiltcoverss - he's conning you into paying for his living costs.
Even if your rent is only £350 a month, and he pays £300, that leaves £125 per month for council tax, house insurance, water, electricity, gas, landline/ internet, food, alcohol, dog food, and it's always a good idea to have a little slush fund for house maintenance, let alone the pet insurance. I'm sorry I can't see £125 covering all of that no matter where you live.
Write down exactly what you pay per month / year for each of the item I've listed - I bet you'll be surprised how much it is. Then divide by 2 - that's what he should be paying. You then need to sit him down, show him the living costs and how much he needs to pay. If he even hesitates a millisecond in agreeing to up his contribution to the amount you've calculated, as much as you love him, he goes, he leaves and he takes his toothbrush with him, (and one of the dogs).
The others are right, if you can't have this conversation, you're not ready yet for a live in relationship