Weed/plant sticky blue sap?

[Skinnywhippet]

Have a bush type plant outside my house. It has medium sized green leaves and the tiny curled leaves in a brighter green colour. Most interestly when I cut it, the sap inside is blue and sticky. What is this? I think it is a weed as it spreads horrendously.

It sounds like a euphorbia, but can you post a picture? Euphorbia sap, though, is usually white and can cause skin irritation.

Is it a weed? I will post pic tomorrow. I let it grow for a few years not realising and now am breaking my back pulling it out!