New to this, and this might be long, sorry.
When I was 17, I had a short fling with a 15 year old boy that resulted in me getting pregnant with twin boys. I was young and stupid (I know) and did lots of dumb stuff, but when I told the father a year after their birth, he wanted to be their dad and asked to be part of their lives. Ex loves the boys, who are now 13. Ex came into a sizeable inheritance when he was 18, and he used part of it to buy the twins and me a house. He is now married and has 4 DC with his wife. I have the boys Monday evening until Friday morning, and during half of the holidays.
Two years ago I met my DP. He moved in to my house a while ago, but he's recently mentioned he'd like me to move out and buy a house with him. This is a bit of a point of contention, but I digress. I love DP, but I'm not sure the boys like him, and I feel that they have been manipulating their father into getting me to try break things off with me.
Last time we spoke ex said DP sounded 'controlling' and wondered whether the relationship was a good one. He got quite annoyed when he found out DP wanted me to move, and we've had a few arguments about this. According to him it's all about the kids, but I feel like he's trying to tell me what to do and it's making me resent him!
Last night it all came to a head and I'm so angry and upset
Twins are on holiday with their father atm and he called yesterday, screaming down the telephone that I need to leave my 'excuse of a man DP' as he's fucking with my kids heads. One of my twins has told us recently that he thinks he might be gay, and he's told his father that DP has been calling him derogatory names when I'm not around. Now apparently I am to be a horrible mother if I don't leave him. We had a blazing row over the phone, and eventually I just hung up on him and cried. DP is visiting family so isn't home, and I don't know whether to believe what my son has said. He's nearly 14 and hasn't been keen on me having a partner from the start, so part of me is worried that he's trying to drive a wedge between everyone. I just don't know what I should be doing. I want to call DP, but I'm just not in a good place right now, and I feel there's nobody on my side. My DC are my everything, but I feel so alone right now and I'm wishing I'd never gotten pregnant, as my life has been so bloody complicated since then. And now I just feel awful sad I know DP is about to propose as well, so there's all these things and they're overwhelming me and I don't know what I should be doing. I feel like my ex has it all figured out and I am just eternally being punished for being young and stupid that one time. 
Sorry if that was long, it's hard to explain my situation and I'm finding things difficult to process atm.